<PAGE>

    As filed with the Securities and Exchange Commission on January 20, 2000
                                                    REGISTRATION NO.
-----------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                             ----------------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                             ----------------------
                                   ECOLAB INC.
             (Exact name of registrant as specified in its charter)
          DELAWARE                                            41-0231510
(State or other jurisdiction of                            (I.R.S. Employer
incorporation or organization)                            Identification No.)

                             ----------------------
                                  Ecolab Center
                            370 North Wabasha Street
                            St. Paul, Minnesota 55102
                                 (651) 293-2233
               (Address, including zip code, and telephone number,
            including area code, of registrant's principal executive
                                    offices)

                             ----------------------
                           ECOLAB MIRROR SAVINGS PLAN
                            (Full title of the plan)

                             ----------------------
                            KENNETH A. IVERSON, ESQ.
                          VICE PRESIDENT AND SECRETARY
                                   ECOLAB INC.
                                  ECOLAB CENTER
                            370 NORTH WABASHA STREET
                            ST. PAUL, MINNESOTA 55102
                                 (651) 293-2125
              (Name and address, including zip code, and telephone
               number, including area code, of agent for service)

                             ----------------------
                  APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED
                              SALE TO THE PUBLIC:
           IMMEDIATELY UPON THE FILING OF THIS REGISTRATION STATEMENT

                             ----------------------
                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>

----------------------------------------------------------------------------------------------------------------------------------
                                                                PROPOSED MAXIMUM             PROPOSED MAXIMUM           AMOUNT OF
        TITLE OF SECURITIES              AMOUNT TO BE            OFFERING PRICE                  AGGREGATE            REGISTRATION
        TO BE REGISTERED (1)              REGISTERED             PER OBLIGATION             OFFERING PRICE (2)             FEE
----------------------------------------------------------------------------------------------------------------------------------
<S>                                       <C>                    <C>                        <C>                       <C>
Deferred Compensation Obligations         $7,500,000                  100%                      $7,500,000               $1,980.00
----------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)      The Deferred Compensation Obligations are unsecured obligations of the
         Registrant to pay deferred compensation in the future in accordance
         with the terms of the Ecolab Mirror Savings Plan. See "Description of
         Securities" herein.

(2)      Estimated solely for the purpose of determining the registration fee.

<PAGE>

                                   PART II

                              INFORMATION REQUIRED
                          IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents filed by Ecolab Inc. (the "Company" or the
"Registrant") (File No.1- 9328) with the Securities and Exchange Commission
(the "Commission") are incorporated by reference in this Registration
Statement: (1) Annual Report on Form 10-K for the year ended December 31,
1998; (2) Quarterly Reports on Form 10-Q for the quarters ended March 31,
June 30 and September 30, 1999; (3) Current Report on Form 8-K dated March
25, 1999; and (4) all other reports filed by the Company pursuant to Sections
13(a) or 15(d) of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), since December 31, 1998.

         All documents filed by the Company pursuant to Sections 13(a),
13(c), 14 or 15(d) of the Exchange Act subsequent to the date hereof and
prior to the termination of the offering of the securities registered
pursuant to this Registration Statement shall be deemed to be incorporated by
reference into this Registration Statement and to be part hereof from the
date of filing of such documents.

         The consolidated financial statements and related financial
statement schedule of the Company, which are included or incorporated by
reference in the Company's Annual Report on Form 10-K for the year ended
December 31, 1998, and incorporated by reference in this Registration
Statement, have been audited by PricewaterhouseCoopers LLP, independent
accountants, for the periods indicated in such firm's reports thereon. The
consolidated financial statements and financial statement schedule audited by
PricewaterhouseCoopers LLP have been incorporated herein by reference in
reliance on such firm's reports given upon their authority as experts in
accounting and auditing. To the extent that PricewaterhouseCoopers LLP
examines and reports on the financial statements and financial statement
schedules of the Company issued at future dates, and consents to the use of
their reports thereon, such financial statements and financial statement
schedules will also be incorporated by reference in this Registration
Statement in reliance upon their reports and said authority.

         With respect to unaudited interim financial information incorporated
by reference in this Registration Statement, PricewaterhouseCoopers LLP has
reported that they have applied limited procedures in accordance with
professional standards for reviews of such information. However, their
separate reports, incorporated by reference herein, state that they did not
audit and they do not express an opinion on that interim financial
information. Accordingly, the degree of reliance on their reports on such
information should be restricted in light of the limited nature of the review
procedures applied. The independent accountants are not subject to the
liability provisions of Section 11 of the Securities Act of 1933 (the
"Securities Act") for their reports on the unaudited interim financial
information because each such report is not a "report" or a "part" of the
Registration Statement prepared or certified by the independent accountants
within the meaning of Sections 7 and 11 of the Securities Act.

         In addition, the combined financial statements and related financial
statement schedule of the Henkel-Ecolab Joint Venture as of November 30, 1998
and for the year ended November 30, 1998, which are included in the Company's
Annual Report on Form 10-K for the year ended December 31, 1998, and
incorporated by reference in this Registration Statement, have been audited
by PricewaterhouseCoopers

                                       2

<PAGE>

Gesellschaft mit beschrankter Haftung Wirtschaftsprufungsgesellschaft,
independent accountants. The combined financial statements and related
financial statement schedule audited by PricewaterhouseCoopers Gesellschaft
mit beschrankter Haftung Wirtschaftsprufungsgesellschaft have been
incorporated herein by reference in reliance on such firm's reports given
upon their authority as experts in accounting and auditing. To the extent
that PricewaterhouseCoopers Gesellschaft mit beschrankter Haftung
Wirtschaftsprufungsgesellschaft examines and reports on the financial
statements and financial statement schedules of the Henkel-Ecolab Joint
Venture issued at future dates, and consents to the use of their reports
thereon, such financial statements and financial statement schedules will
also be incorporated by reference in this Registration Statement in reliance
upon their reports and said authority.

         In addition, the combined balance sheets of the Henkel-Ecolab Joint
Venture as of November 30, 1997 and 1996, and the related combined statements
of income, equity and cash flows for each of the periods beginning December
1, 1996 and 1995 and ended November 30, 1997 and 1996, respectively, and
related financial statement schedule for the same periods (collectively, the
"1996 and 1997 Henkel-Ecolab Joint Venture Financials"), which are included
in the Company's Annual Report on Form 10-K for the year ended December 31,
1998, and incorporated by reference in this Registration Statement, have been
audited by KPMG Deutsche Treuhand-Gesellschaft Aktiengesellschaft
Wirtschaftsprufungsgesellschaft, independent accountants. The 1996 and 1997
Henkel-Ecolab Joint Venture Financials audited by KPMG Deutsche
Treuhand-Gesellschaft Aktiengesellschaft Wirtschaftsprufungsgesellschaft have
been incorporated herein by reference in reliance on such firm's reports
given upon their authority as experts in accounting and auditing.

ITEM 4.  DESCRIPTION OF SECURITIES.

         Under the Ecolab Mirror Savings (the "Plan"), the Registrant and
certain subsidiaries will provide deferred compensation benefits to certain
management and highly compensated employees of the Registrant and such
subsidiaries that are in addition to those provided under the Ecolab Savings
Plan (the "Savings Plan"). The Registrant and such subsidiaries will
partially match deferrals made by employees participating in the Plan
("Employer Matching Contribution"). Both the employee deferrals and the
Employer Matching Contributions are credited to individual accounts
("Accounts") established and maintained on the books of the Registrant or
such subsidiary in the name of each participating employee. The obligations
of the Registrant to its participating employees, as well as the obligations
of certain of its subsidiaries to the participating employees of such
subsidiaries, to the extent such subsidiary obligations have been guaranteed
by the Registrant (collectively the "Deferred Compensation Obligations"),
which are represented by the Accounts will be unsecured general obligations
of the Registrant to pay deferred compensation in the future in accordance
with the terms of the Plan and will rank pari passu with other unsecured and
unsubordinated indebtedness of the Registrant from time to time outstanding.

         The amount of compensation to be deferred by each participating
employee will be determined in accordance with the Plan based on elections by
the employee. Each Deferred Compensation Obligation will be payable by the
Registrant in accordance with the terms of the Plan. All employee deferrals
and Employer Matching Contributions will be deemed to have been invested in
one or more Hypothetical Investment Funds. Under this arrangement, the
Deferred Compensation Obligations are indexed to such Hypothetical Investment
Funds and are adjusted to reflect the investment experience of the
Hypothetical Investment Funds, including any appreciation or depreciation.
The yield of the Hypothetical Investment Funds corresponds to that of certain
investment funds that are designated from time to time by the Registrant for
investment of deferred compensation proceeds under the Savings Plan. One of
the investment funds so designated invests primarily

                                       3

<PAGE>

in the Common Stock of the Registrant.

         An employee participant's right or the right of any other person to
the Deferred Compensation Obligations cannot be assigned, alienated, sold,
garnished, transferred, pledged or encumbered except (i) by a written
designation of a beneficiary under the Plan, (ii) by written will, (iii) by
the laws of descent and distribution or (iv) by an Internal Revenue Service
levy for unpaid taxes.

         The Deferred Compensation Obligations are not subject to redemption,
in whole or in part, prior to the payment dates specified in the Plan, except
in limited circumstances where total or partial redemption may, in the sole
discretion of the Plan Administrator, be necessary in order to alleviate the
consequences of an unforeseen emergency faced by the participating employee.
However, the Registrant reserves the right to amend or terminate the Plan at
any time, except that no such amendment or termination shall adversely affect
the right of an employee participant to the balance of his or her Account as
of the date of such amendment or termination.

         The Deferred Compensation Obligations are not convertible into any
other security of the Registrant. The Deferred Compensation Obligations will
not have the benefit of a negative pledge or any other affirmative or
negative covenant on the part of the Registrant. No trustee has been
appointed having the authority to take action with respect to the Deferred
Compensation Obligations, and each employee participant will be responsible
for acting independently with respect to, among other things, the giving of
notice, responding to any requests for consents, waivers or amendments
pertaining to the Deferred Compensation Obligations, enforcing covenants and
taking action upon default.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

         Kenneth A. Iverson, Vice President and Secretary of the Company, who
has passed upon the legality of the Deferred Compensation Obligations offered
hereby, is eligible for participation in the Plan.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Subsection (a) of Section 145 of the General Corporation Law of
Delaware ("DGCL") empowers a corporation to indemnify any person who was or
is a party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative
or investigative (other than an action by or in the right of the
corporation), by reason of the fact that such person is or was a director,
officer, employee or agent of the corporation or is or was serving at the
request of the corporation as a director, officer, employee or agent of
another corporation or enterprise, against expenses (including attorneys'
fees), judgments, fines and amounts paid in settlement actually and
reasonably incurred by such person in connection with such action, suit or
proceeding if such person acted in good faith and in a manner such person
reasonably believed to be in or not opposed to the best interests of the
corporation, and with respect to any criminal action or proceeding, had no
reasonable cause to believe such person's conduct was unlawful.

         Subsection (b) of Section 145 empowers a corporation to indemnify
any person who was or is a party or threatened to be made a party to any
threatened, pending or completed action or suit by or in the right of the
corporation to procure a judgment in its favor by reason of the fact that
such person acted in any of the capacities set forth above, against expenses
actually and reasonably incurred by such person in connection with the
defense or settlement of such action or suit if such person acted under
similar standards, except that

                                       4

<PAGE>

no indemnification may be made in respect of any claim, issue or matter as to
which such person shall have been adjudged to be liable to the corporation
unless and only to the extent that the Court of Chancery or the court in
which such action or suit was brought shall determine that, despite the
adjudication of liability, such person is fairly and reasonably entitled to
indemnity for such expenses which the court shall deem proper.

         Section 145 further provides that, to the extent a director or
officer of a corporation has been successful in the defense of any action,
suit or proceeding referred to in subsections (a) and (b) or in the defense
of any claim, issue or matter therein, such person shall be indemnified
against expenses (including attorneys' fees) actually and reasonably incurred
in connection therewith; that indemnification provided for by Section 145
shall not be deemed exclusive of any other rights to which the indemnified
party may be entitled; and that the scope of indemnification extends to
directors, officers, employees or agents of a constituent corporation
absorbed in a consolidation or merger and persons serving in that capacity at
the request of the constituent corporation for another. Section 145 also
empowers the corporation to purchase and maintain insurance on behalf of a
director or officer of the corporation against any liability asserted against
or incurred by such person in any such capacity or arising out of such
person's status as such, whether or not the corporation would have the power
to indemnify such person against such liabilities under Section 145,
including liabilities under the Securities Act.

         Article V of the Company's By-Laws provides for indemnification of
the Company's officers and directors to the full extent allowed by the DGCL.

         In addition, Article IV of the Company's Restated Certificate of
Incorporation provides that the Company's directors do not have personal
liability to the Company or its stockholders for monetary damages for any
breach of their fiduciary duty as directors, except (i) for a breach of the
duty of loyalty, (ii) for acts or omissions not in good faith or which
involve intentional misconduct or knowing violation of the law, (iii) for
willful or negligent violations of certain provisions under the DGCL imposing
certain requirements with respect to stock repurchases, redemptions and
dividends, or (iv) for any transaction from which the director derived an
improper personal benefit. Subject to these exceptions, under Article IV,
directors do not have any personal liability to the Company or its
stockholders for any violation of their fiduciary duty.

         The Company has directors and officers liability insurance which
protects each director or officer from certain claims and suits, including
stockholder derivative suits, even where the director may be determined to
not be entitled to indemnification under the DGCL and claims and suits
arising under the Securities Act. The policy may also afford coverage under
circumstances where the facts do not justify a finding that the director or
officer acted in good faith and in a manner that was in or not opposed to the
best interests of the Company.

         The Company has entered into indemnification agreements with each of
its directors (the "Indemnification Agreements"). The Indemnification
Agreements provide for the prompt indemnification "to the fullest extent
permitted by law" and for the prompt advancement of expenses, including
attorneys' fees and other costs, expenses and obligations paid or incurred in
connection with investigating, defending, being a witness or participating in
(including on appeal) any threatened, pending or completed action, suit or
proceeding related to the fact that such director is or was a director,
officer, employee, trustee, agent or fiduciary of the Company or is or was
serving at the request of the Company as a director, officer, employee,
trustee, agent or fiduciary of another corporation, partnership, joint
venture, employee benefit plan trust or other enterprise, or by reason of
anything done or not done by a director in any such capacity. The
Indemnification Agreements further provide that the Company has the burden of
proving that a director is

                                       5

<PAGE>

not entitled to indemnification in any particular case.

         The foregoing represents a summary of the general effect of the
DGCL, the Company's By-Laws and Restated Certificate of Incorporation, the
Company's directors and officers liability insurance coverage and the
Indemnification Agreements for purposes of general description only.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable - no securities are to be re-offered or resold
pursuant to this Registration Statement.

ITEM 8.  EXHIBITS.


4.1      Restated Certificate of Incorporation of the Company (incorporated by
         reference to Exhibit (3) to the Company's Current Report on Form 8-K
         dated October 22, 1997).
4.2      Bylaws of the Company, as amended through February 18, 1999
         (incorporated by reference to Exhibit 3(B) to the Company's Annual
         Report on Form 10-K for the year ended December 31, 1998 (File
         No.1-9328)).
4.3      Form of Common Stock Certificate (incorporated by reference to Exhibit
         4(B) to the Company's Annual Report on Form 10-K for the year ended
         December 31, 1995 (File No. 1-9328)).
4.4      Rights Agreement, dated as of February 24, 1996, between the Company
         and First Chicago Trust Company of New York, as Rights Agent
         (incorporated by reference to Exhibit 4 to the Company's Current Report
         on Form 8-K dated February 24, 1996 (File No. 1-9328)).
5.1      Opinion and Consent of Kenneth A. Iverson (filed herewith
         electronically).
15.1     Letter of PricewaterhouseCoopers LLP regarding unaudited interim
         financial information (filed herewith electronically).
23.1     Consent of PricewaterhouseCoopers LLP (filed herewith electronically).
23.2     Consent of PricewaterhouseCoopers GmbH (filed herewith electronically).
23.3     Consent of KPMG Deutsche Treuhand-Gesellschaft Aktiengesellschaft
         Wirtschaftsprufungsgesellschaft (filed herewith electronically).
24.1     Powers of Attorney (filed herewith electronically).

ITEM 9.  UNDERTAKINGS.

         The undersigned Registrant hereby undertakes:

         (1)      To file, during any period in which offers or sales are being
                  made, a post-effective amendment to this registration
                  statement:

                  (i)      To include any prospectus required by Section
                           10(a)(3) of the Securities Act;

                  (ii)     To reflect in the prospectus any facts or events
                           arising after the effective date of the registration
                           statement (or the most recent post-effective
                           amendment thereof) which, individually or in the
                           aggregate, represent a fundamental change in the
                           information set forth in the registration statement.
                           Notwithstanding the foregoing, any increase or
                           decrease in volume of securities offered (if the
                           total dollar value of securities offered would not
                           exceed that which was registered) and any deviation
                           from the low or high end of the estimated maximum
                           offering range may be reflected in the

                                        6

<PAGE>

                           form of prospectus filed with the Commission
                           pursuant to Rule 424(b) under the Securities
                           Act if, in the aggregate, the changes in volume
                           and price represent no more than a 20% change
                           in the maximum aggregate offering price set forth
                           in the "Calculation of Registration Fee" table
                           in the effective registration statement;


                  (iii)    To include any material information with respect to
                           the plan of distribution not previously disclosed in
                           the registration statement or any material change to
                           such information in the registration statement;

                           PROVIDED, HOWEVER, that paragraphs (1)(i) and (1)(ii)
                  do not apply if the information required to be included in a
                  post-effective amendment by those paragraphs is contained in
                  periodic reports filed with or furnished to the Commission by
                  the Registrant pursuant to Section 13 or Section 15(d) of the
                  Exchange Act that are incorporated by reference in the
                  registration statement.

         (2)      That, for the purpose of determining any liability under the
                  Securities Act, each such post-effective amendment shall be
                  deemed to be a new registration statement relating to the
                  securities offered therein, and the offering of such
                  securities at that time shall be deemed to be the initial bona
                  fide offering thereof.

         (3)      To remove from registration by means of a post-effective
                  amendment any of the securities being registered which remain
                  unsold at the termination of the offering.

         The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the registration statement shall be deemed to be
a new registration statement relating to the securities offered therein, and
the offering of such securities at that time shall be deemed to be the
initial bona fide offering thereof.

         Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling
persons of the Registrant, the Registrant has been advised that in the
opinion of the Commission such indemnification is against public policy as
expressed in the Securities Act and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than
the payment by the Registrant of expenses incurred or paid by a director,
officer or controlling person of the Registrant in the successful defense of
any action, suit or proceeding) is asserted by such director, officer or
controlling person in connection with the securities being registered, the
Registrant will, unless in the opinion of its counsel the matter has been
settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against
public policy as expressed in the Securities Act and will be governed by the
final adjudication of such issue.

                                      7

<PAGE>

                                   SIGNATURES

THE REGISTRANT. Pursuant to the requirements of the Securities Act of 1933,
the Registrant certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
registration statement to be signed on its behalf by the undersigned,
thereunto duly authorized, in the City of St. Paul, State of Minnesota, on
January 20, 2000.

                                   ECOLAB INC.


                                   By:/s/ Allan L. Schuman
                                      ------------------------------
                                      Allan L. Schuman
                                      Chairman of the Board, President and Chief
                                      Executive Officer


         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed on January 20, 2000 by the following
persons in the capacities indicated.

<TABLE>

<S>                                             <C>
/s/ Allan L. Schuman                            Chairman of the Board, President and Chief Executive
-------------------------------                 Officer (Principal Executive Officer) and Director
Allan L. Schuman


/s/ L. White Matthews, III                      Executive Vice President and Chief Financial
------------------------------                  Officer (Principal Financial Officer) and Director
L. White Matthews, III


/s/ Steven L. Fritze                            Vice President and Controller (Principal
------------------------------                  Accounting Officer)
Steven L. Fritze


/Ss/ Kenneth A. Iverson                         Directors
------------------------------
Kenneth A. Iverson, as attorney-in-fact for
Les S. Biller, Ruth S. Block, Jerry A.
Grundhofer, James J. Howard, William L.
Jews, Joel W. Johnson, Jerry W. Levin, Robert
L. Lumpkins, Richard L. Schall, Roland
Schulz, Hugo Uyterhoeven and Albrecht Woeste

Director not signing: Reuben F. Richards
</TABLE>

                                       8

<PAGE>

                                INDEX TO EXHIBITS
<TABLE>
<CAPTION>

ITEM        DESCRIPTION                                                   METHOD OF FILING
NO.         -----------                                                   ----------------
----
<S>         <C>                                                <C>
4.1         Restated Certificate of Incorporation of           Incorporated by reference to Exhibit (3) to
            the Company....................................    the Company's Current Report on Form 8-K
                                                               dated October 22, 1997.

4.2         Bylaws of the Company, as amended                  Incorporated by reference to Exhibit 3(B)
            through February 18, 1999 .....................    to the Company's Annual Report on Form 10-K
                                                               for the year ended December 31, 1999 (File
                                                               No.1-9328).

4.3         Form of Common Stock Certificate........,,,,,,,    Incorporated by reference to  Exhibit
                                                               4(B) to the Company's Annual Report on Form
                                                               10-K for the year ended December 31, 1995
                                                               (File No. 1-9328).

4.4         Rights Agreement, dated as of February             Incorporated by reference to Exhibit 4 to
            24, 1996, between the Company and                  the Company's Current Report on Form 8-K
            First Chicago Trust Company of New                 dated February 24, 1996.
            York, as Rights Agent..........................

5.1         Opinion and Consent of Kenneth A.
            Iverson........................................    Filed herewith electronically.

15.1        Letter of PricewaterhouseCoopers LLP
            regarding unaudited interim financial
            information....................................    Filed herewith electronically.

23.1        Consent of PricewaterhouseCoopers
            LLP............................................    Filed herewith electronically.

23.2        Consent of PricewaterhouseCoopers
            GmbH ..........................................    Filed herewith electronically.

23.3        Consent of KPMG Deutsche Treuhand- Gesellschaft
            Aktiengesellschaft
            Wirtschaftsprufungsgesellschaft................    Filed herewith electronically.

24.1        Powers of Attorney.............................    Filed herewith electronically.
</TABLE>
                                       9
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 32133}]
{"company-data": {"conformed-name": "ECOLAB INC", "cik": "0000031462", "assigned-sic": "2840", "irs-number": "410231510", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-95037", "film-number": "510337"}, "business-address": {"street1": "ECOLAB CTR", "street2": "370 N WABASHA ST", "city": "ST PAUL", "state": "MN", "zip": "55102", "phone": "6122932233"}, "former-company": {"former-conformed-name": "ECONOMICS LABORATORY INC", "date-changed": "19861203"}}
As filed with the Securities and Exchange Commission on January 20, 2000
                                                    REGISTRATION NO.
-----------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                             ----------------------
                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                             ----------------------
                                   ECOLAB INC.
             (Exact name of registrant as specified in its charter)
          DELAWARE                                            41-0231510
(State or other jurisdiction of                            (I.R.S. Employer
incorporation or organization)                            Identification No.)

                             ----------------------
                                  Ecolab Center
                            370 North Wabasha Street
                            St. Paul, Minnesota 55102
                                 (651) 293-2233
               (Address, including zip code, and telephone number,
            including area code, of registrant's principal executive
                                    offices)

                             ----------------------
                           ECOLAB MIRROR SAVINGS PLAN
                            (Full title of the plan)

                             ----------------------
                            KENNETH A. IVERSON, ESQ.
                          VICE PRESIDENT AND SECRETARY
                                   ECOLAB INC.
                                  ECOLAB CENTER
                            370 NORTH WABASHA STREET
                            ST. PAUL, MINNESOTA 55102
                                 (651) 293-2125
              (Name and address, including zip code, and telephone
               number, including area code, of agent for service)

                             ----------------------
                  APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED
                              SALE TO THE PUBLIC:
           IMMEDIATELY UPON THE FILING OF THIS REGISTRATION STATEMENT

                             ----------------------
                         CALCULATION OF REGISTRATION FEE
----------------------------------------------------------------------------------------------------------------------------------
                                                                PROPOSED MAXIMUM             PROPOSED MAXIMUM           AMOUNT OF
        TITLE OF SECURITIES              AMOUNT TO BE            OFFERING PRICE                  AGGREGATE            REGISTRATION
        TO BE REGISTERED (1)              REGISTERED             PER OBLIGATION             OFFERING PRICE (2)             FEE
----------------------------------------------------------------------------------------------------------------------------------
Deferred Compensation Obligations         $7,500,000                  100%                      $7,500,000               $1,980.00
----------------------------------------------------------------------------------------------------------------------------------
(1)      The Deferred Compensation Obligations are unsecured obligations of the
         Registrant to pay deferred compensation in the future in accordance
         with the terms of the Ecolab Mirror Savings Plan. See "Description of
         Securities" herein.

(2)      Estimated solely for the purpose of determining the registration fee.
PART II

                              INFORMATION REQUIRED
                          IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents filed by Ecolab Inc. (the "Company" or the
"Registrant") (File No.1- 9328) with the Securities and Exchange Commission
(the "Commission") are incorporated by reference in this Registration
Statement: (1) Annual Report on Form 10-K for the year ended December 31,
1998; (2) Quarterly Reports on Form 10-Q for the quarters ended March 31,
June 30 and September 30, 1999; (3) Current Report on Form 8-K dated March
25, 1999; and (4) all other reports filed by the Company pursuant to Sections
13(a) or 15(d) of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), since December 31, 1998.

         All documents filed by the Company pursuant to Sections 13(a),
13(c), 14 or 15(d) of the Exchange Act subsequent to the date hereof and
prior to the termination of the offering of the securities registered
pursuant to this Registration Statement shall be deemed to be incorporated by
reference into this Registration Statement and to be part hereof from the
date of filing of such documents.

         The consolidated financial statements and related financial
statement schedule of the Company, which are included or incorporated by
reference in the Company's Annual Report on Form 10-K for the year ended
December 31, 1998, and incorporated by reference in this Registration
Statement, have been audited by PricewaterhouseCoopers LLP, independent
accountants, for the periods indicated in such firm's reports thereon. The
consolidated financial statements and financial statement schedule audited by
PricewaterhouseCoopers LLP have been incorporated herein by reference in
reliance on such firm's reports given upon their authority as experts in
accounting and auditing. To the extent that PricewaterhouseCoopers LLP
examines and reports on the financial statements and financial statement
schedules of the Company issued at future dates, and consents to the use of
their reports thereon, such financial statements and financial statement
schedules will also be incorporated by reference in this Registration
Statement in reliance upon their reports and said authority.

         With respect to unaudited interim financial information incorporated
by reference in this Registration Statement, PricewaterhouseCoopers LLP has
reported that they have applied limited procedures in accordance with
professional standards for reviews of such information. However, their
separate reports, incorporated by reference herein, state that they did not
audit and they do not express an opinion on that interim financial
information. Accordingly, the degree of reliance on their reports on such
information should be restricted in light of the limited nature of the review
procedures applied. The independent accountants are not subject to the
liability provisions of Section 11 of the Securities Act of 1933 (the
"Securities Act") for their reports on the unaudited interim financial
information because each such report is not a "report" or a "part" of the
Registration Statement prepared or certified by the independent accountants
within the meaning of Sections 7 and 11 of the Securities Act.

         In addition, the combined financial statements and related financial
statement schedule of the Henkel-Ecolab Joint Venture as of November 30, 1998
and for the year ended November 30, 1998, which are included in the Company's
Annual Report on Form 10-K for the year ended December 31, 1998, and
incorporated by reference in this Registration Statement, have been audited
by PricewaterhouseCoopers

                                       2
Gesellschaft mit beschrankter Haftung Wirtschaftsprufungsgesellschaft,
independent accountants. The combined financial statements and related
financial statement schedule audited by PricewaterhouseCoopers Gesellschaft
mit beschrankter Haftung Wirtschaftsprufungsgesellschaft have been
incorporated herein by reference in reliance on such firm's reports given
upon their authority as experts in accounting and auditing. To the extent
that PricewaterhouseCoopers Gesellschaft mit beschrankter Haftung
Wirtschaftsprufungsgesellschaft examines and reports on the financial
statements and financial statement schedules of the Henkel-Ecolab Joint
Venture issued at future dates, and consents to the use of their reports
thereon, such financial statements and financial statement schedules will
also be incorporated by reference in this Registration Statement in reliance
upon their reports and said authority.

         In addition, the combined balance sheets of the Henkel-Ecolab Joint
Venture as of November 30, 1997 and 1996, and the related combined statements
of income, equity and cash flows for each of the periods beginning December
1, 1996 and 1995 and ended November 30, 1997 and 1996, respectively, and
related financial statement schedule for the same periods (collectively, the
"1996 and 1997 Henkel-Ecolab Joint Venture Financials"), which are included
in the Company's Annual Report on Form 10-K for the year ended December 31,
1998, and incorporated by reference in this Registration Statement, have been
audited by KPMG Deutsche Treuhand-Gesellschaft Aktiengesellschaft
Wirtschaftsprufungsgesellschaft, independent accountants. The 1996 and 1997
Henkel-Ecolab Joint Venture Financials audited by KPMG Deutsche
Treuhand-Gesellschaft Aktiengesellschaft Wirtschaftsprufungsgesellschaft have
been incorporated herein by reference in reliance on such firm's reports
given upon their authority as experts in accounting and auditing.

ITEM 4.  DESCRIPTION OF SECURITIES.

         Under the Ecolab Mirror Savings (the "Plan"), the Registrant and
certain subsidiaries will provide deferred compensation benefits to certain
management and highly compensated employees of the Registrant and such
subsidiaries that are in addition to those provided under the Ecolab Savings
Plan (the "Savings Plan"). The Registrant and such subsidiaries will
partially match deferrals made by employees participating in the Plan
("Employer Matching Contribution"). Both the employee deferrals and the
Employer Matching Contributions are credited to individual accounts
("Accounts") established and maintained on the books of the Registrant or
such subsidiary in the name of each participating employee. The obligations
of the Registrant to its participating employees, as well as the obligations
of certain of its subsidiaries to the participating employees of such
subsidiaries, to the extent such subsidiary obligations have been guaranteed
by the Registrant (collectively the "Deferred Compensation Obligations"),
which are represented by the Accounts will be unsecured general obligations
of the Registrant to pay deferred compensation in the future in accordance
with the terms of the Plan and will rank pari passu with other unsecured and
unsubordinated indebtedness of the Registrant from time to time outstanding.

         The amount of compensation to be deferred by each participating
employee will be determined in accordance with the Plan based on elections by
the employee. Each Deferred Compensation Obligation will be payable by the
Registrant in accordance with the terms of the Plan. All employee deferrals
and Employer Matching Contributions will be deemed to have been invested in
one or more Hypothetical Investment Funds. Under this arrangement, the
Deferred Compensation Obligations are indexed to such Hypothetical Investment
Funds and are adjusted to reflect the investment experience of the
Hypothetical Investment Funds, including any appreciation or depreciation.
The yield of the Hypothetical Investment Funds corresponds to that of certain
investment funds that are designated from time to time by the Registrant for
investment of deferred compensation proceeds under the Savings Plan. One of
the investment funds so designated invests primarily

                                       3
in the Common Stock of the Registrant.

         An employee participant's right or the right of any other person to
the Deferred Compensation Obligations cannot be assigned, alienated, sold,
garnished, transferred, pledged or encumbered except (i) by a written
designation of a beneficiary under the Plan, (ii) by written will, (iii) by
the laws of descent and distribution or (iv) by an Internal Revenue Service
levy for unpaid taxes.

         The Deferred Compensation Obligations are not subject to redemption,
in whole or in part, prior to the payment dates specified in the Plan, except
in limited circumstances where total or partial redemption may, in the sole
discretion of the Plan Administrator, be necessary in order to alleviate the
consequences of an unforeseen emergency faced by the participating employee.
However, the Registrant reserves the right to amend or terminate the Plan at
any time, except that no such amendment or termination shall adversely affect
the right of an employee participant to the balance of his or her Account as
of the date of such amendment or termination.

         The Deferred Compensation Obligations are not convertible into any
other security of the Registrant. The Deferred Compensation Obligations will
not have the benefit of a negative pledge or any other affirmative or
negative covenant on the part of the Registrant. No trustee has been
appointed having the authority to take action with respect to the Deferred
Compensation Obligations, and each employee participant will be responsible
for acting independently with respect to, among other things, the giving of
notice, responding to any requests for consents, waivers or amendments
pertaining to the Deferred Compensation Obligations, enforcing covenants and
taking action upon default.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

         Kenneth A. Iverson, Vice President and Secretary of the Company, who
has passed upon the legality of the Deferred Compensation Obligations offered
hereby, is eligible for participation in the Plan.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Subsection (a) of Section 145 of the General Corporation Law of
Delaware ("DGCL") empowers a corporation to indemnify any person who was or
is a party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative
or investigative (other than an action by or in the right of the
corporation), by reason of the fact that such person is or was a director,
officer, employee or agent of the corporation or is or was serving at the
request of the corporation as a director, officer, employee or agent of
another corporation or enterprise, against expenses (including attorneys'
fees), judgments, fines and amounts paid in settlement actually and
reasonably incurred by such person in connection with such action, suit or
proceeding if such person acted in good faith and in a manner such person
reasonably believed to be in or not opposed to the best interests of the
corporation, and with respect to any criminal action or proceeding, had no
reasonable cause to believe such person's conduct was unlawful.

         Subsection (b) of Section 145 empowers a corporation to indemnify
any person who was or is a party or threatened to be made a party to any
threatened, pending or completed action or suit by or in the right of the
corporation to procure a judgment in its favor by reason of the fact that
such person acted in any of the capacities set forth above, against expenses
actually and reasonably incurred by such person in connection with the
defense or settlement of such action or suit if such person acted under
similar standards, except that

                                       4
no indemnification may be made in respect of any claim, issue or matter as to
which such person shall have been adjudged to be liable to the corporation
unless and only to the extent that the Court of Chancery or the court in
which such action or suit was brought shall determine that, despite the
adjudication of liability, such person is fairly and reasonably entitled to
indemnity for such expenses which the court shall deem proper.

         Section 145 further provides that, to the extent a director or
officer of a corporation has been successful in the defense of any action,
suit or proceeding referred to in subsections (a) and (b) or in the defense
of any claim, issue or matter therein, such person shall be indemnified
against expenses (including attorneys' fees) actually and reasonably incurred
in connection therewith; that indemnification provided for by Section 145
shall not be deemed exclusive of any other rights to which the indemnified
party may be entitled; and that the scope of indemnification extends to
directors, officers, employees or agents of a constituent corporation
absorbed in a consolidation or merger and persons serving in that capacity at
the request of the constituent corporation for another. Section 145 also
empowers the corporation to purchase and maintain insurance on behalf of a
director or officer of the corporation against any liability asserted against
or incurred by such person in any such capacity or arising out of such
person's status as such, whether or not the corporation would have the power
to indemnify such person against such liabilities under Section 145,
including liabilities under the Securities Act.

         Article V of the Company's By-Laws provides for indemnification of
the Company's officers and directors to the full extent allowed by the DGCL.

         In addition, Article IV of the Company's Restated Certificate of
Incorporation provides that the Company's directors do not have personal
liability to the Company or its stockholders for monetary damages for any
breach of their fiduciary duty as directors, except (i) for a breach of the
duty of loyalty, (ii) for acts or omissions not in good faith or which
involve intentional misconduct or knowing violation of the law, (iii) for
willful or negligent violations of certain provisions under the DGCL imposing
certain requirements with respect to stock repurchases, redemptions and
dividends, or (iv) for any transaction from which the director derived an
improper personal benefit. Subject to these exceptions, under Article IV,
directors do not have any personal liability to the Company or its
stockholders for any violation of their fiduciary duty.

         The Company has directors and officers liability insurance which
protects each director or officer from certain claims and suits, including
stockholder derivative suits, even where the director may be determined to
not be entitled to indemnification under the DGCL and claims and suits
arising under the Securities Act. The policy may also afford coverage under
circumstances where the facts do not justify a finding that the director or
officer acted in good faith and in a manner that was in or not opposed to the
best interests of the Company.

         The Company has entered into indemnification agreements with each of
its directors (the "Indemnification Agreements"). The Indemnification
Agreements provide for the prompt indemnification "to the fullest extent
permitted by law" and for the prompt advancement of expenses, including
attorneys' fees and other costs, expenses and obligations paid or incurred in
connection with investigating, defending, being a witness or participating in
(including on appeal) any threatened, pending or completed action, suit or
proceeding related to the fact that such director is or was a director,
officer, employee, trustee, agent or fiduciary of the Company or is or was
serving at the request of the Company as a director, officer, employee,
trustee, agent or fiduciary of another corporation, partnership, joint
venture, employee benefit plan trust or other enterprise, or by reason of
anything done or not done by a director in any such capacity. The
Indemnification Agreements further provide that the Company has the burden of
proving that a director is

                                       5
not entitled to indemnification in any particular case.

         The foregoing represents a summary of the general effect of the
DGCL, the Company's By-Laws and Restated Certificate of Incorporation, the
Company's directors and officers liability insurance coverage and the
Indemnification Agreements for purposes of general description only.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable - no securities are to be re-offered or resold
pursuant to this Registration Statement.

ITEM 8.  EXHIBITS.

4.1      Restated Certificate of Incorporation of the Company (incorporated by
         reference to Exhibit (3) to the Company's Current Report on Form 8-K
         dated October 22, 1997).
4.2      Bylaws of the Company, as amended through February 18, 1999
         (incorporated by reference to Exhibit 3(B) to the Company's Annual
         Report on Form 10-K for the year ended December 31, 1998 (File
         No.1-9328)).
4.3      Form of Common Stock Certificate (incorporated by reference to Exhibit
         4(B) to the Company's Annual Report on Form 10-K for the year ended
         December 31, 1995 (File No. 1-9328)).
4.4      Rights Agreement, dated as of February 24, 1996, between the Company
         and First Chicago Trust Company of New York, as Rights Agent
         (incorporated by reference to Exhibit 4 to the Company's Current Report
         on Form 8-K dated February 24, 1996 (File No. 1-9328)).
5.1      Opinion and Consent of Kenneth A. Iverson (filed herewith
         electronically).
15.1     Letter of PricewaterhouseCoopers LLP regarding unaudited interim
         financial information (filed herewith electronically).
23.1     Consent of PricewaterhouseCoopers LLP (filed herewith electronically).
23.2     Consent of PricewaterhouseCoopers GmbH (filed herewith electronically).
23.3     Consent of KPMG Deutsche Treuhand-Gesellschaft Aktiengesellschaft
         Wirtschaftsprufungsgesellschaft (filed herewith electronically).
24.1     Powers of Attorney (filed herewith electronically).

ITEM 9.  UNDERTAKINGS.

         The undersigned Registrant hereby undertakes:

         (1)      To file, during any period in which offers or sales are being
                  made, a post-effective amendment to this registration
                  statement:

                  (i)      To include any prospectus required by Section
                           10(a)(3) of the Securities Act;

                  (ii)     To reflect in the prospectus any facts or events
                           arising after the effective date of the registration
                           statement (or the most recent post-effective
                           amendment thereof) which, individually or in the
                           aggregate, represent a fundamental change in the
                           information set forth in the registration statement.
                           Notwithstanding the foregoing, any increase or
                           decrease in volume of securities offered (if the
                           total dollar value of securities offered would not
                           exceed that which was registered) and any deviation
                           from the low or high end of the estimated maximum
                           offering range may be reflected in the

                                        6
form of prospectus filed with the Commission
                           pursuant to Rule 424(b) under the Securities
                           Act if, in the aggregate, the changes in volume
                           and price represent no more than a 20% change
                           in the maximum aggregate offering price set forth
                           in the "Calculation of Registration Fee" table
                           in the effective registration statement;

                  (iii)    To include any material information with respect to
                           the plan of distribution not previously disclosed in
                           the registration statement or any material change to
                           such information in the registration statement;

                           PROVIDED, HOWEVER, that paragraphs (1)(i) and (1)(ii)
                  do not apply if the information required to be included in a
                  post-effective amendment by those paragraphs is contained in
                  periodic reports filed with or furnished to the Commission by
                  the Registrant pursuant to Section 13 or Section 15(d) of the
                  Exchange Act that are incorporated by reference in the
                  registration statement.

         (2)      That, for the purpose of determining any liability under the
                  Securities Act, each such post-effective amendment shall be
                  deemed to be a new registration statement relating to the
                  securities offered therein, and the offering of such
                  securities at that time shall be deemed to be the initial bona
                  fide offering thereof.

         (3)      To remove from registration by means of a post-effective
                  amendment any of the securities being registered which remain
                  unsold at the termination of the offering.

         The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit
plan's annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in the registration statement shall be deemed to be
a new registration statement relating to the securities offered therein, and
the offering of such securities at that time shall be deemed to be the
initial bona fide offering thereof.

         Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling
persons of the Registrant, the Registrant has been advised that in the
opinion of the Commission such indemnification is against public policy as
expressed in the Securities Act and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than
the payment by the Registrant of expenses incurred or paid by a director,
officer or controlling person of the Registrant in the successful defense of
any action, suit or proceeding) is asserted by such director, officer or
controlling person in connection with the securities being registered, the
Registrant will, unless in the opinion of its counsel the matter has been
settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against
public policy as expressed in the Securities Act and will be governed by the
final adjudication of such issue.

                                      7
SIGNATURES

THE REGISTRANT. Pursuant to the requirements of the Securities Act of 1933,
the Registrant certifies that it has reasonable grounds to believe that it
meets all of the requirements for filing on Form S-8 and has duly caused this
registration statement to be signed on its behalf by the undersigned,
thereunto duly authorized, in the City of St. Paul, State of Minnesota, on
January 20, 2000.

                                   ECOLAB INC.

                                   By:/s/ Allan L. Schuman
                                      ------------------------------
                                      Allan L. Schuman
                                      Chairman of the Board, President and Chief
                                      Executive Officer

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed on January 20, 2000 by the following
persons in the capacities indicated.
/s/ Allan L. Schuman                            Chairman of the Board, President and Chief Executive
-------------------------------                 Officer (Principal Executive Officer) and Director
Allan L. Schuman

/s/ L. White Matthews, III                      Executive Vice President and Chief Financial
------------------------------                  Officer (Principal Financial Officer) and Director
L. White Matthews, III

/s/ Steven L. Fritze                            Vice President and Controller (Principal
------------------------------                  Accounting Officer)
Steven L. Fritze

/Ss/ Kenneth A. Iverson                         Directors
------------------------------
Kenneth A. Iverson, as attorney-in-fact for
Les S. Biller, Ruth S. Block, Jerry A.
Grundhofer, James J. Howard, William L.
Jews, Joel W. Johnson, Jerry W. Levin, Robert
L. Lumpkins, Richard L. Schall, Roland
Schulz, Hugo Uyterhoeven and Albrecht Woeste

Director not signing: Reuben F. Richards
8
INDEX TO EXHIBITS
ITEM        DESCRIPTION                                                   METHOD OF FILING
NO.         -----------                                                   ----------------
----
4.1         Restated Certificate of Incorporation of           Incorporated by reference to Exhibit (3) to
            the Company....................................    the Company's Current Report on Form 8-K
                                                               dated October 22, 1997.

4.2         Bylaws of the Company, as amended                  Incorporated by reference to Exhibit 3(B)
            through February 18, 1999 .....................    to the Company's Annual Report on Form 10-K
                                                               for the year ended December 31, 1999 (File
                                                               No.1-9328).

4.3         Form of Common Stock Certificate........,,,,,,,    Incorporated by reference to  Exhibit
                                                               4(B) to the Company's Annual Report on Form
                                                               10-K for the year ended December 31, 1995
                                                               (File No. 1-9328).

4.4         Rights Agreement, dated as of February             Incorporated by reference to Exhibit 4 to
            24, 1996, between the Company and                  the Company's Current Report on Form 8-K
            First Chicago Trust Company of New                 dated February 24, 1996.
            York, as Rights Agent..........................

5.1         Opinion and Consent of Kenneth A.
            Iverson........................................    Filed herewith electronically.

15.1        Letter of PricewaterhouseCoopers LLP
            regarding unaudited interim financial
            information....................................    Filed herewith electronically.

23.1        Consent of PricewaterhouseCoopers
            LLP............................................    Filed herewith electronically.

23.2        Consent of PricewaterhouseCoopers
            GmbH ..........................................    Filed herewith electronically.

23.3        Consent of KPMG Deutsche Treuhand- Gesellschaft
            Aktiengesellschaft
            Wirtschaftsprufungsgesellschaft................    Filed herewith electronically.

24.1        Powers of Attorney.............................    Filed herewith electronically.
9