As filed with the Securities and Exchange Commission on September 25, 2003
                              Registration No. 33-


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM S-8


                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933


                              IONICS, INCORPORATED
             (Exact name of registrant as specified in its charter)


      Massachusetts                                      04-2068530
(State of incorporation)                    (IRS employer identification number)



                                 65 Grove Street
                       Watertown, Massachusetts 02472-2882
              (Address and zip code of principal executive offices)


                    IONICS SECTION 401(k) STOCK SAVINGS PLAN
                            (Full title of the Plan)


                               Stephen Korn, Esq.
                        Vice President & General Counsel
                              Ionics, Incorporated
                                 65 Grove Street
                       Watertown, Massachusetts 02472-2882
                     (Name and address of agent for service)


                                  617-926-2500
          (Telephone number, including area code, of agent for service)




                                       1
<PAGE>
<TABLE>
<CAPTION>



                                                    CALCULATION OF REGISTRATION FEE

      <S>                                           <C>               <C>                  <C>             <C>
                                                                       Proposed            Proposed
                                                                       Maximum              Maximum           Amount of
                                                    Amount to be     Offering Price        Aggregate       Registration
      Title of Securities to be Registered          Registered (1)     Per Share          Offering Price        Fee
      ------------------------------------          --------------     ---------          --------------        ---

    Common Stock (Par Value $1.00 Per Share)           900,000          $27.93(2)        $25,137,000       $2,033.58

                      Total                            900,000            $27.93         $25,137,000       $2,033.58
---------------
</TABLE>

(1)      In addition, pursuant to Rule 416(c) under the Securities Act of 1933,
         this Registration Statement also covers an indeterminate amount of
         interests to be offered or sold pursuant to the Ionics Section 401(k)
         Stock Savings Plan described herein.

(2)      The offering price per share of Common Shares registered hereunder
         shall be determined at time of sale. Accordingly, pursuant to Rule
         457(c) and Rule 457(h) under the Securities Act of 1933, the price of
         $27.93 per share, which is the average of the high and low prices
         reported on the New York Stock Exchange on September 22, 2003, is set
         forth solely for purposes of calculating the registration fee.





                                       2
<PAGE>



                                     PART I


Item 1.    Plan Information

           The documents containing the information specified in this Item 1
           will be sent or given to participants in the Ionics Section 401(k)
           Stock Savings Plan, as specified by Rule 428(b)(1). In accordance
           with the rules and regulations of the Securities and Exchange
           Commission (the "Commission") and the instructions to Form S-8, such
           documents are not being filed with the Commission either as part of
           this Registration Statement or as prospectuses or prospectus
           supplements pursuant to Rule 424.

Item 2.    Registrant Information and Employee Plan Annual Information

           The documents containing the information specified in this Item 2
           will be sent or given to participants as specified by Rule 428(b)(1).
           In accordance with the rules and regulations of the Commission and
           the instructions to Form S-8, such documents are not being filed with
           the Commission either as part of this Registration Statement or as
           prospectuses or prospectus supplements pursuant to Rule 424.


                                     PART II


               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.    Incorporation of Documents by Reference

           The following documents filed with the Commission are incorporated by
reference in this Prospectus:

     (a)  (1) The Annual Report of Ionics,  Incorporated (the "Company") on Form
          10-K for the  fiscal  year ended  December  31,  2002,  filed with the
          Commission  on  March  31,  2003,  which  contains  audited  financial
          statements of the Company for the fiscal year ended December 31, 2002,
          as amended by Form 10-K/A filed with the Commission on April 1, 2003.

          (2)  The Annual Report of the Ionics Section 401(k) Stock Savings Plan
               on Form 11-K for the fiscal year ended  December 31, 2002,  filed
               with  the  Commission  on Form  10-K/A  on June 24,  2003,  which
               contains  audited  financial  statements  of the  Ionics  Section
               401(k) Stock Savings Plan for the year ended December 31, 2002.

     (b)  (1) The Quarterly Report of Ionics,  Incorporated on Form 10-Q for the
          fiscal quarter ended March 31, 2003,  filed with the Commission on May
          15, 2003.


          (2)  The Quarterly Report of Ionics, Incorporated on Form 10-Q for the
               fiscal quarter ended June 30, 2003,  filed with the Commission on
               August 13, 2003.

           (c)    The section entitled "Description of Registrant's Securities
                  to be Registered" contained in The Company's Registration
                  Statement on Form 8-A, filed with the Commission on September
                  27, 1990 pursuant to Section 12(g) of the Exchange Act.

           All documents subsequently filed with the Commission by the Company,


                                       3
<PAGE>

           the Ionics Section 401(k) Stock Savings Plan, or both, pursuant to
           Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the
           filing of a post-effective amendment which indicates that all
           securities offered herein have been sold or which deregisters all
           securities then remaining unsold, shall be deemed to be incorporated
           by reference in this Registration Statement and to be a part hereof
           from the date of filing such documents.

Item 4.    Description of Securities

           Not applicable.

Item 5.    Interest of Named Experts and Counsel

           The validity of the shares of Common Stock offered hereby will be
           passed upon for the Registrant by Stephen Korn, Esq., Vice President
           and General Counsel of the Company. Mr. Korn is the beneficial owner
           of 128,814 shares of Common Stock, including 126,000 shares of Common
           Stock in the form of presently exercisable stock options and 1,591
           shares held in the Ionics Section 401(k) Stock Savings Plan (based on
           August 31, 2003 data).

Item 6.    Indemnification of Directors and Officers

           The Company is permitted by Massachusetts law and required by its
           By-laws to indemnify any director or officer or former director or
           officer against all expenses and liabilities reasonably incurred by
           him in connection with any legal action in which such person is
           involved by reason of his position with the Company unless he shall
           have been finally adjudicated in any action, suit or proceeding not
           to have acted in good faith in the reasonable belief that his action
           was in the best interests of the Company. Such indemnification shall
           include payment by the Company of expenses incurred in defending a
           civil or criminal action or proceeding in advance of the final
           disposition of such action or proceeding, upon the Company's receipt
           of the undertaking of the person indemnified to repay such payment if
           such person shall be adjudicated not entitled to such
           indemnification.

           Directors and officers are also insured up to an aggregate amount of
           $15 million under Directors' and Officers' Liability and Company
           Reimbursement Policies.

           The Company's Restated Articles of Organization include a provision
           limiting the personal liability of directors of the Company to its
           stockholders for monetary damages for breaches of their fiduciary
           duty to the extent permitted by the Massachusetts Business
           Corporation Law.

Item 7.    Exemption from Registration Claimed

           Not applicable.

Item 8.    Exhibits

           The securities being registered hereby are not original issuance
           securities. Accordingly, no opinion of counsel as to the legality of
           such securities is being furnished herewith.

           The Company has submitted the Ionics Section 401(k) Stock Savings
           Plan (2002 Amendment and Restatement) to the Internal Revenue Service
           ("IRS") in a timely manner, and undertakes to submit any amendments
           thereto to the IRS in a timely manner. The Company further undertakes
           to make all changes required by the IRS in order to qualify such plan
           under Section 401 of the Internal Revenue Code.



                                       4
<PAGE>




           Exhibit No.       Description of Exhibit

           *4.1              Renewed Rights Agreement, dated as of August 19,
                             1997, between the Company and BankBoston N.A.
                             (filed as Exhibit 1 to the Company's Current Report
                             on Form 8-K dated August 27, 1997).

           *4.2              Form of Common Stock Certificate (filed as Exhibit
                             4.2 to the Company's Annual Report on Form 10-K for
                             the year ended December 31, 1995).

           4.3               Ionics Section 401(k) Stock Savings Plan (2002
                             Amendment and Restatement), as amended.

           23.1              Consent of PricewaterhouseCoopers LLP.

           23.2              Consent of Belanger & Company, P.C.

           24.0              Power of Attorney.

*Incorporated herein by reference.

Item 9.    Undertakings

(a)  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 of 1933;

          (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;

          (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  (a)(1)(i) and (a)(1)(ii) do not
          apply if the registration statement is on Form S-3 or Form S-8 and 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  Securities  Exchange  Act of 1934  that are
          incorporated by reference in the Registration Statement.

     (2)  That,  for  the  purpose  of  determining   any  liability  under  the
          Securities Act of 1933,  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.



                                       5
<PAGE>




(b)  The  undersigned   Registrant  hereby  undertakes  that,  for  purposes  of
     determining  any liability under the Securities Act of 1933, each filing of
     the  Registrant's  annual report  pursuant to Section 13(a) or 15(d) of the
     Securities  Exchange Act of 1934 (and, where applicable,  each filing of an
     employee  benefit  plan's  annual  report  pursuant to Section 15(d) of the
     Securities  Exchange Act of 1934) 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.

(c)  Insofar as indemnification for liabilities arising under the Securities Act
     of 1933 may be permitted to directors, officers, and controlling persons of
     the  Registrant  pursuant to the foregoing  provisions,  or otherwise,  the
     Registrant  has been  advised  that in the  opinion of the  Securities  and
     Exchange  Commission  such  indemnification  is  against  public  policy as
     expressed in the 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 Act and will be  governed by the final
     adjudication of such issue.

                                   SIGNATURES

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 Town of Watertown and  Commonwealth of  Massachusetts on the
25th day of September, 2003.

                                          IONICS, INCORPORATED

                                   By:    /s/Douglas R. Brown
                                          Douglas R. Brown
                                          President and Chief Executive Officer

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

   Signature                              Title                     Date

                                  President and
                             Chief Executive Officer
/s/ Douglas R. Brown        (Principal Executive Officer)    September 25, 2003
--------------------
Douglas R. Brown

                               Vice President and
                             Chief Financial Officer
/s/ Daniel M. Kuzmak       (Principal Financial Officer)     September 25, 2003
--------------------
Daniel M. Kuzmak

                               Vice President and
                              Corporate Controller
/s/ Anthony DiPaola        (Principal Accounting Officer)    September 25, 2003
-------------------
Anthony DiPaola




                                       6
<PAGE>



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


Date: September 25, 2003            Director               /s/Douglas R. Brown
                                                           -------------------
                                                           Douglas R. Brown

Date: September 25, 2003            Director               /s/Stephen L. Brown
                                                           -------------------
                                                           Stephen L. Brown

                              Chairman of the Board
Date: September 25, 2003         and Director             /s/Arthur L. Goldstein
                                                          ----------------------
                                                          Arthur L. Goldstein

Date:                               Director
                                                          Kathleen F. Feldstein

Date: September 25, 2003            Director               /s/William K. Reilly
                                                           --------------------
                                                           William K. Reilly

Date: September 25, 2003            Director               /s/John J. Shields
                                                           ------------------
                                                           John J. Shields

Date: September 25, 2003            Director               /s/Daniel I. C. Wang
                                                           --------------------
                                                           Daniel I. C. Wang

Date: September 25, 2003            Director               /s/Mark S. Wrighton
                                                           -------------------
                                                           Mark S. Wrighton

Date: September 25, 2003            Director               /s/Allen S. Wyett
                                                           -----------------
                                                           Allen S. Wyett



                                       7
<PAGE>

<TABLE>
<CAPTION>


                                  EXHIBIT INDEX

                                                                                     Sequentially Numbered
Exhibit No.                         Description of Exhibits                                 Page
<S>              <C>                                                                 <C>

4.1              Renewed Rights Agreement, dated as of August 19, 1997, between                 *
                 the Company and BankBoston N.A. (filed as Exhibit 1 to the
                 Company's Current Report on Form 8-K dated August 27, 1997).

4.2              Form of Common Stock Certificate (filed as Exhibit 4.2 to the                  *
                 Company's Annual Report on Form 10-K for the year ended December
                 31, 1995).

4.3              Ionics Section 401(k) Stock Savings Plan (2002 Amendment and
                 Restatement), as amended.

23.1             Consent of PricewaterhouseCoopers LLP.

23.2             Consent of Belanger & Company, P.C.

24.0             Power of Attorney

*Incorporated herein by reference.
</TABLE>

                                       8
<PAGE>
[{"type": "S-8", "sequence": "1", "filename": "forms8-stockplan.txt", "secsgml_size_bytes": 20362}]
{"company-data": {"conformed-name": "IONICS INC", "cik": "0000052466", "assigned-sic": "3559", "irs-number": "042068530", "state-of-incorporation": "MA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-109103", "film-number": "03909270"}, "business-address": {"street1": "65 GROVE ST", "city": "WATERTOWN", "state": "MA", "zip": "02172", "phone": "6179262500"}}
As filed with the Securities and Exchange Commission on September 25, 2003
                              Registration No. 33-

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8

                          REGISTRATION STATEMENT UNDER
                           THE SECURITIES ACT OF 1933

                              IONICS, INCORPORATED
             (Exact name of registrant as specified in its charter)

      Massachusetts                                      04-2068530
(State of incorporation)                    (IRS employer identification number)

                                 65 Grove Street
                       Watertown, Massachusetts 02472-2882
              (Address and zip code of principal executive offices)

                    IONICS SECTION 401(k) STOCK SAVINGS PLAN
                            (Full title of the Plan)

                               Stephen Korn, Esq.
                        Vice President & General Counsel
                              Ionics, Incorporated
                                 65 Grove Street
                       Watertown, Massachusetts 02472-2882
                     (Name and address of agent for service)

                                  617-926-2500
          (Telephone number, including area code, of agent for service)

                                       1
CALCULATION OF REGISTRATION FEE
Proposed            Proposed
                                                                       Maximum              Maximum           Amount of
                                                    Amount to be     Offering Price        Aggregate       Registration
      Title of Securities to be Registered          Registered (1)     Per Share          Offering Price        Fee
      ------------------------------------          --------------     ---------          --------------        ---

    Common Stock (Par Value $1.00 Per Share)           900,000          $27.93(2)        $25,137,000       $2,033.58

                      Total                            900,000            $27.93         $25,137,000       $2,033.58
---------------
(1)      In addition, pursuant to Rule 416(c) under the Securities Act of 1933,
         this Registration Statement also covers an indeterminate amount of
         interests to be offered or sold pursuant to the Ionics Section 401(k)
         Stock Savings Plan described herein.

(2)      The offering price per share of Common Shares registered hereunder
         shall be determined at time of sale. Accordingly, pursuant to Rule
         457(c) and Rule 457(h) under the Securities Act of 1933, the price of
         $27.93 per share, which is the average of the high and low prices
         reported on the New York Stock Exchange on September 22, 2003, is set
         forth solely for purposes of calculating the registration fee.

                                       2
PART I

Item 1.    Plan Information

           The documents containing the information specified in this Item 1
           will be sent or given to participants in the Ionics Section 401(k)
           Stock Savings Plan, as specified by Rule 428(b)(1). In accordance
           with the rules and regulations of the Securities and Exchange
           Commission (the "Commission") and the instructions to Form S-8, such
           documents are not being filed with the Commission either as part of
           this Registration Statement or as prospectuses or prospectus
           supplements pursuant to Rule 424.

Item 2.    Registrant Information and Employee Plan Annual Information

           The documents containing the information specified in this Item 2
           will be sent or given to participants as specified by Rule 428(b)(1).
           In accordance with the rules and regulations of the Commission and
           the instructions to Form S-8, such documents are not being filed with
           the Commission either as part of this Registration Statement or as
           prospectuses or prospectus supplements pursuant to Rule 424.

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.    Incorporation of Documents by Reference

           The following documents filed with the Commission are incorporated by
reference in this Prospectus:

     (a)  (1) The Annual Report of Ionics,  Incorporated (the "Company") on Form
          10-K for the  fiscal  year ended  December  31,  2002,  filed with the
          Commission  on  March  31,  2003,  which  contains  audited  financial
          statements of the Company for the fiscal year ended December 31, 2002,
          as amended by Form 10-K/A filed with the Commission on April 1, 2003.

          (2)  The Annual Report of the Ionics Section 401(k) Stock Savings Plan
               on Form 11-K for the fiscal year ended  December 31, 2002,  filed
               with  the  Commission  on Form  10-K/A  on June 24,  2003,  which
               contains  audited  financial  statements  of the  Ionics  Section
               401(k) Stock Savings Plan for the year ended December 31, 2002.

     (b)  (1) The Quarterly Report of Ionics,  Incorporated on Form 10-Q for the
          fiscal quarter ended March 31, 2003,  filed with the Commission on May
          15, 2003.

          (2)  The Quarterly Report of Ionics, Incorporated on Form 10-Q for the
               fiscal quarter ended June 30, 2003,  filed with the Commission on
               August 13, 2003.

           (c)    The section entitled "Description of Registrant's Securities
                  to be Registered" contained in The Company's Registration
                  Statement on Form 8-A, filed with the Commission on September
                  27, 1990 pursuant to Section 12(g) of the Exchange Act.

           All documents subsequently filed with the Commission by the Company,

                                       3
the Ionics Section 401(k) Stock Savings Plan, or both, pursuant to
           Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the
           filing of a post-effective amendment which indicates that all
           securities offered herein have been sold or which deregisters all
           securities then remaining unsold, shall be deemed to be incorporated
           by reference in this Registration Statement and to be a part hereof
           from the date of filing such documents.

Item 4.    Description of Securities

           Not applicable.

Item 5.    Interest of Named Experts and Counsel

           The validity of the shares of Common Stock offered hereby will be
           passed upon for the Registrant by Stephen Korn, Esq., Vice President
           and General Counsel of the Company. Mr. Korn is the beneficial owner
           of 128,814 shares of Common Stock, including 126,000 shares of Common
           Stock in the form of presently exercisable stock options and 1,591
           shares held in the Ionics Section 401(k) Stock Savings Plan (based on
           August 31, 2003 data).

Item 6.    Indemnification of Directors and Officers

           The Company is permitted by Massachusetts law and required by its
           By-laws to indemnify any director or officer or former director or
           officer against all expenses and liabilities reasonably incurred by
           him in connection with any legal action in which such person is
           involved by reason of his position with the Company unless he shall
           have been finally adjudicated in any action, suit or proceeding not
           to have acted in good faith in the reasonable belief that his action
           was in the best interests of the Company. Such indemnification shall
           include payment by the Company of expenses incurred in defending a
           civil or criminal action or proceeding in advance of the final
           disposition of such action or proceeding, upon the Company's receipt
           of the undertaking of the person indemnified to repay such payment if
           such person shall be adjudicated not entitled to such
           indemnification.

           Directors and officers are also insured up to an aggregate amount of
           $15 million under Directors' and Officers' Liability and Company
           Reimbursement Policies.

           The Company's Restated Articles of Organization include a provision
           limiting the personal liability of directors of the Company to its
           stockholders for monetary damages for breaches of their fiduciary
           duty to the extent permitted by the Massachusetts Business
           Corporation Law.

Item 7.    Exemption from Registration Claimed

           Not applicable.

Item 8.    Exhibits

           The securities being registered hereby are not original issuance
           securities. Accordingly, no opinion of counsel as to the legality of
           such securities is being furnished herewith.

           The Company has submitted the Ionics Section 401(k) Stock Savings
           Plan (2002 Amendment and Restatement) to the Internal Revenue Service
           ("IRS") in a timely manner, and undertakes to submit any amendments
           thereto to the IRS in a timely manner. The Company further undertakes
           to make all changes required by the IRS in order to qualify such plan
           under Section 401 of the Internal Revenue Code.

                                       4
Exhibit No.       Description of Exhibit

           *4.1              Renewed Rights Agreement, dated as of August 19,
                             1997, between the Company and BankBoston N.A.
                             (filed as Exhibit 1 to the Company's Current Report
                             on Form 8-K dated August 27, 1997).

           *4.2              Form of Common Stock Certificate (filed as Exhibit
                             4.2 to the Company's Annual Report on Form 10-K for
                             the year ended December 31, 1995).

           4.3               Ionics Section 401(k) Stock Savings Plan (2002
                             Amendment and Restatement), as amended.

           23.1              Consent of PricewaterhouseCoopers LLP.

           23.2              Consent of Belanger & Company, P.C.

           24.0              Power of Attorney.

*Incorporated herein by reference.

Item 9.    Undertakings

(a)  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 of 1933;

          (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;

          (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  (a)(1)(i) and (a)(1)(ii) do not
          apply if the registration statement is on Form S-3 or Form S-8 and 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  Securities  Exchange  Act of 1934  that are
          incorporated by reference in the Registration Statement.

     (2)  That,  for  the  purpose  of  determining   any  liability  under  the
          Securities Act of 1933,  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.

                                       5
(b)  The  undersigned   Registrant  hereby  undertakes  that,  for  purposes  of
     determining  any liability under the Securities Act of 1933, each filing of
     the  Registrant's  annual report  pursuant to Section 13(a) or 15(d) of the
     Securities  Exchange Act of 1934 (and, where applicable,  each filing of an
     employee  benefit  plan's  annual  report  pursuant to Section 15(d) of the
     Securities  Exchange Act of 1934) 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.

(c)  Insofar as indemnification for liabilities arising under the Securities Act
     of 1933 may be permitted to directors, officers, and controlling persons of
     the  Registrant  pursuant to the foregoing  provisions,  or otherwise,  the
     Registrant  has been  advised  that in the  opinion of the  Securities  and
     Exchange  Commission  such  indemnification  is  against  public  policy as
     expressed in the 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 Act and will be  governed by the final
     adjudication of such issue.

                                   SIGNATURES

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 Town of Watertown and  Commonwealth of  Massachusetts on the
25th day of September, 2003.

                                          IONICS, INCORPORATED

                                   By:    /s/Douglas R. Brown
                                          Douglas R. Brown
                                          President and Chief Executive Officer

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

   Signature                              Title                     Date

                                  President and
                             Chief Executive Officer
/s/ Douglas R. Brown        (Principal Executive Officer)    September 25, 2003
--------------------
Douglas R. Brown

                               Vice President and
                             Chief Financial Officer
/s/ Daniel M. Kuzmak       (Principal Financial Officer)     September 25, 2003
--------------------
Daniel M. Kuzmak

                               Vice President and
                              Corporate Controller
/s/ Anthony DiPaola        (Principal Accounting Officer)    September 25, 2003
-------------------
Anthony DiPaola

                                       6
Pursuant to the requirements of the Securities Act of 1933, this Registration
Statement has been signed by the following persons in the capacities and on the
date indicated.

Date: September 25, 2003            Director               /s/Douglas R. Brown
                                                           -------------------
                                                           Douglas R. Brown

Date: September 25, 2003            Director               /s/Stephen L. Brown
                                                           -------------------
                                                           Stephen L. Brown

                              Chairman of the Board
Date: September 25, 2003         and Director             /s/Arthur L. Goldstein
                                                          ----------------------
                                                          Arthur L. Goldstein

Date:                               Director
                                                          Kathleen F. Feldstein

Date: September 25, 2003            Director               /s/William K. Reilly
                                                           --------------------
                                                           William K. Reilly

Date: September 25, 2003            Director               /s/John J. Shields
                                                           ------------------
                                                           John J. Shields

Date: September 25, 2003            Director               /s/Daniel I. C. Wang
                                                           --------------------
                                                           Daniel I. C. Wang

Date: September 25, 2003            Director               /s/Mark S. Wrighton
                                                           -------------------
                                                           Mark S. Wrighton

Date: September 25, 2003            Director               /s/Allen S. Wyett
                                                           -----------------
                                                           Allen S. Wyett

                                       7
EXHIBIT INDEX

                                                                                     Sequentially Numbered
Exhibit No.                         Description of Exhibits                                 Page
4.1              Renewed Rights Agreement, dated as of August 19, 1997, between                 *
                 the Company and BankBoston N.A. (filed as Exhibit 1 to the
                 Company's Current Report on Form 8-K dated August 27, 1997).

4.2              Form of Common Stock Certificate (filed as Exhibit 4.2 to the                  *
                 Company's Annual Report on Form 10-K for the year ended December
                 31, 1995).

4.3              Ionics Section 401(k) Stock Savings Plan (2002 Amendment and
                 Restatement), as amended.

23.1             Consent of PricewaterhouseCoopers LLP.

23.2             Consent of Belanger & Company, P.C.

24.0             Power of Attorney

*Incorporated herein by reference.
8