Registration No. 333-______
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                MALLINCKRODT INC.
                       (formerly Mallinckrodt Group Inc.)
             (Exact name of Registrant as specified in its charter)

         New York                  675 McDonnell Boulevard      36-1263901
(State or other jurisdiction of        P.O. Box 5840         (I.R.S. Employer
incorporation or organization)      St. Louis, MO 63134     Identification No.)
                                     (314) 654-2000
                            (Address of principal executive
                                         offices)

                        INVESTMENT PLAN FOR EMPLOYEES OF
                                MALLINCKRODT INC.
                              (Full Title of Plan)
                              ---------------------

                                 Roger A. Keller
                   Vice President, Secretary & General Counsel
                                Mallinckrodt Inc.
                             675 McDonnell Boulevard
                                  P.O. Box 5840
                               St. Louis, MO 63134
                                 (314) 654-2000
                      (Name, address and telephone number,
                   including area code, of agent for service)
                              ---------------------

                                   Copies to:
                               John M. Reiss, Esq.
                                White & Case LLP
                           1155 Avenue of the Americas
                            New York, New York 10036
                                 (212) 819-8200
                              ---------------------
<TABLE>
                         CALCULATION OF REGISTRATION FEE

==================================================================================================================
<CAPTION>
                                                        Proposed maximum     Proposed maximum        Amount of
     Title of securities to be         Amount to be      offering price     aggregate offering   registration fee
            registered                  registered        per share <F1>       price <F1>
            ----------                  ----------        -------------         ---------
<S>                                    <C>              <C>                 <C>                  <C>
Common Stock, $1.00 par value......     1,000,000           $32.65625            $32,656,250          $9078.44
==================================================================================================================

(1)   Estimated  solely for the purpose of calculating the  registration  fee in
      accordance  with Rule 457(h) and 457(c) under the  Securities Act of 1933,
      based upon the  average of the high and low prices of the Common  Stock as
      reported on the New York Stock Exchange, Inc. on August 18, 1999.

(2)   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  employee  benefit  plan
      described herein.
</TABLE>
<PAGE>
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


Item 3.   Incorporation of Documents by Reference.

          This Registration  Statement  registers  additional  securities of the
same class as other securities for which a registration  statement filed on this
form  relating  to the same  stock  purchase  plan is  effective.  Consequently,
pursuant to General  Instruction E of Form S-8, the contents of the registration
statement on Form S-8 filed by Mallinckrodt  Inc. with respect to the Investment
Plan for Employees of Mallinckrodt  Inc.,  registration  statement No. 333-34489
(which in turn incorporated by reference the contents of registration  statement
No. 2-94151, as amended) are incorporated herein by reference.

Item 8.   Exhibits

Exhibit
Number            Description of Documents
------            ------------------------

5(a)           Opinion  of  Roger  A.  Keller  as  to  legality  of   securities
               (including Consent).

5(b)           Determination letter from Internal Revenue Service dated February
               10,  1986.  Incorporated  herein by  reference to Exhibit 5(c) to
               Post-Effective   Amendment  No.  3,  Registration  Statement  No.
               2-94151.

23.1           Consent of Ernst & Young LLP.

23.2           Consent of Stone Carlie & Company, L.L.C.

23.3           Consent of Roger A. Keller included in Exhibit 5(a).

24             Power of Attorney of certain officers and directors  (included on
               pages II-2 through II-4) and Power of Attorney of certain members
               of the  Employee  Benefits  Committee  (included  on  pages  II-4
               through II-5).
<PAGE>

                                   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  City of St.  Louis,  State of  Missouri, on the 18th day of
August, 1999.

                                           MALLINCKRODT INC.

                                           By /s/ C. Ray Holman
                                             ---------------------------------
                                             Name:    C. Ray Holman
                                             Title:   Chairman of the Board and
                                                        Chief Executive Officer


                                POWER OF ATTORNEY

          KNOW ALL MEN BY THESE  PRESENTS,  that  each  person  whose  signature
appears below  constitutes  and appoints C. Ray Holman and Roger A. Keller,  and
each of them severally,  his true and lawful  attorneys-in-fact and agents, with
full power of substitution  and  resubstitution,  for him and in his name, place
and stead, in any and all capacities,  to sign any and all amendments (including
post-effective amendments) to this Registration Statement, and to file the same,
with all exhibits thereto, and other documents in connection therewith, with the
Securities and Exchange  Commission,  granting unto said  attorneys-in-fact  and
agents,  and each of them,  full power and  authority to do and perform each and
every act and thing requisite or necessary to be done in and about the premises,
as fully to all intents and  purposes as he might or could do in person,  hereby
ratifying and confirming all that said attorneys-in-fact and agents or either of
them, or their or his substitute or substitutes,  may lawfully do or cause to be
done by virtue  hereof.  This Power of  Attorney  may be executed in one or more
counterparts.

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


/s/ C. Ray Holman                                 Chairman of the Board and
--------------------------------                  Chief Executive Officer
C. Ray Holman
Date:  August 18, 1999

/s/ Michael A. Rocca                              Senior Vice President and
--------------------------------                  Chief Financial Officer
Michael A. Rocca                                  (Principal Financial
Date:  August 18, 1999                            Officer)

/s/ Douglas A. McKinney                           Vice President and
--------------------------------                  Controller (Principal
Douglas A. McKinney                               Accounting Officer)
Date:  August 18, 1999

/s/ Raymond F. Bentele                            Director
--------------------------------
Raymond F. Bentele
Date:  August 18, 1999

/s/ Gareth C.C. Chang                             Director
--------------------------------
Gareth C.C. Chang
Date:  August 18, 1999

/s/ William L. Davis, III                         Director
--------------------------------
William L. Davis, III
Date:  August 18, 1999

/s/ Ronald G. Evens                               Director
--------------------------------
Ronald G. Evens
Date:  August 18, 1999

/s/ Roberta S. Karmel                             Director
--------------------------------
Roberta S. Karmel
Date:  August 18, 1999

/s/ Claudine B. Malone                            Director
--------------------------------
Claudine B. Malone
Date:  August 18, 1999

/s/ Anthony Viscusi                               Director
--------------------------------
Anthony Viscusi
Date:  August 18, 1999

/s/ Brian M. Rushton                              Director
--------------------------------
Brian M. Rushton
Date:  August 18, 1999

/s/ Daniel R. Toll                                Director
--------------------------------
Daniel R. Toll
Date:  August 18, 1999


          Pursuant  to the  requirements  of the  Securities  Act of  1933,  the
Employee   Benefits   Committee  of  Mallinckrodt  Inc.  has  duly  caused  this
Registration Statement to be signed on its behalf by the undersigned,  thereunto
duly authorized, in the City of St. Louis, State of Missouri, on the 18th day of
August, 1999.



                                              INVESTMENT PLAN FOR EMPLOYEES
                                                OF MALLINCKRODT INC.


                                              /s/ William B. Stone
                                              ----------------------------
                                              Name: William B. Stone
                                              Title: Chairman



                                POWER OF ATTORNEY

          KNOW ALL MEN BY THESE  PRESENTS,  that  each  person  whose  signature
appears below  constitutes  and appoints C. Ray Holman and Roger A. Keller,  and
each of them severally,  his true and lawful  attorneys-in-fact and agents, with
full power of substitution  and  resubstitution,  for him and in his name, place
and stead, in any and all capacities,  to sign any and all amendments (including
post-effective amendments) to this Registration Statement, and to file the same,
with all exhibits thereto, and other documents in connection therewith, with the
Securities and Exchange  Commission,  granting unto said  attorneys-in-fact  and
agents,  and each of them,  full power and  authority to do and perform each and
every act and thing requisite or necessary to be done in and about the premises,
as fully to all intents and  purposes as he might or could do in person,  hereby
ratifying and confirming all that said attorneys-in-fact and agents or either of
them, or their or his substitute or substitutes,  may lawfully do or cause to be
done by virtue  hereof.  This Power of  Attorney  may be executed in one or more
counterparts.

          Pursuant  to the  requirements  of the  Securities  Act of 1933,  this
Registration  Statement has been signed below by the following  persons in their
capacities  as  members  of the  Employee  Benefits  Committee  and on the  date
indicated.

        Signature                                        Date

/s/ Bruce K. Crockett                              August 18, 1999
----------------------------
Bruce K. Crockett

/s/ Roger A. Keller                                August 18, 1999
----------------------------
Roger A. Keller

/s/ David R. Kupferer                              August 18, 1999
----------------------------
David R. Kupferer

/s/ Judith C. Rebholz                              August 18, 1999
----------------------------
Judith C. Rebholz

/s/ John J. Riordan                                August 18, 1999
----------------------------
John J. Riordan

/s/ Nancy J. Stemme                                August 18, 1999
----------------------------
Nancy J. Stemme

/s/ William B. Stone                               August 18, 1999
----------------------------
William B. Stone

/s/ Frank A. Voltolina                             August 18, 1999
----------------------------
Frank A. Voltolina
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{"company-data": {"conformed-name": "MALLINCKRODT INC /MO", "cik": "0000051396", "assigned-sic": "2835", "irs-number": "361263901", "state-of-incorporation": "NY", "fiscal-year-end": "0630"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-85789", "film-number": "99698056"}, "business-address": {"street1": "675 MCDONNELL BLVD", "street2": "PO BOX 5840", "city": "ST LOUIS", "state": "MO", "zip": "63134", "phone": "3146542000"}, "mail-address": {"street1": "7733 FORSYTH BLVD", "city": "ST LOUIS", "state": "MO", "zip": "63105-1820"}, "former-company": [{"former-conformed-name": "MALLINCKRODT INC  /MO", "date-changed": "19970625"}, {"former-conformed-name": "MALLINCKRODT GROUP INC", "date-changed": "19940322"}, {"former-conformed-name": "IMCERA GROUP INC", "date-changed": "19920703"}]}
Registration No. 333-______
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                MALLINCKRODT INC.
                       (formerly Mallinckrodt Group Inc.)
             (Exact name of Registrant as specified in its charter)

         New York                  675 McDonnell Boulevard      36-1263901
(State or other jurisdiction of        P.O. Box 5840         (I.R.S. Employer
incorporation or organization)      St. Louis, MO 63134     Identification No.)
                                     (314) 654-2000
                            (Address of principal executive
                                         offices)

                        INVESTMENT PLAN FOR EMPLOYEES OF
                                MALLINCKRODT INC.
                              (Full Title of Plan)
                              ---------------------

                                 Roger A. Keller
                   Vice President, Secretary & General Counsel
                                Mallinckrodt Inc.
                             675 McDonnell Boulevard
                                  P.O. Box 5840
                               St. Louis, MO 63134
                                 (314) 654-2000
                      (Name, address and telephone number,
                   including area code, of agent for service)
                              ---------------------

                                   Copies to:
                               John M. Reiss, Esq.
                                White & Case LLP
                           1155 Avenue of the Americas
                            New York, New York 10036
                                 (212) 819-8200
                              ---------------------

                         CALCULATION OF REGISTRATION FEE

==================================================================================================================
Proposed maximum     Proposed maximum        Amount of
     Title of securities to be         Amount to be      offering price     aggregate offering   registration fee
            registered                  registered        per share
price
----------                  ----------        -------------         ---------
Common Stock, $1.00 par value......     1,000,000           $32.65625            $32,656,250          $9078.44
==================================================================================================================

(1)   Estimated  solely for the purpose of calculating the  registration  fee in
      accordance  with Rule 457(h) and 457(c) under the  Securities Act of 1933,
      based upon the  average of the high and low prices of the Common  Stock as
      reported on the New York Stock Exchange, Inc. on August 18, 1999.

(2)   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  employee  benefit  plan
      described herein.
PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.   Incorporation of Documents by Reference.

          This Registration  Statement  registers  additional  securities of the
same class as other securities for which a registration  statement filed on this
form  relating  to the same  stock  purchase  plan is  effective.  Consequently,
pursuant to General  Instruction E of Form S-8, the contents of the registration
statement on Form S-8 filed by Mallinckrodt  Inc. with respect to the Investment
Plan for Employees of Mallinckrodt  Inc.,  registration  statement No. 333-34489
(which in turn incorporated by reference the contents of registration  statement
No. 2-94151, as amended) are incorporated herein by reference.

Item 8.   Exhibits

Exhibit
Number            Description of Documents
------            ------------------------

5(a)           Opinion  of  Roger  A.  Keller  as  to  legality  of   securities
               (including Consent).

5(b)           Determination letter from Internal Revenue Service dated February
               10,  1986.  Incorporated  herein by  reference to Exhibit 5(c) to
               Post-Effective   Amendment  No.  3,  Registration  Statement  No.
               2-94151.

23.1           Consent of Ernst & Young LLP.

23.2           Consent of Stone Carlie & Company, L.L.C.

23.3           Consent of Roger A. Keller included in Exhibit 5(a).

24             Power of Attorney of certain officers and directors  (included on
               pages II-2 through II-4) and Power of Attorney of certain members
               of the  Employee  Benefits  Committee  (included  on  pages  II-4
               through II-5).
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  City of St.  Louis,  State of  Missouri, on the 18th day of
August, 1999.

                                           MALLINCKRODT INC.

                                           By /s/ C. Ray Holman
                                             ---------------------------------
                                             Name:    C. Ray Holman
                                             Title:   Chairman of the Board and
                                                        Chief Executive Officer

                                POWER OF ATTORNEY

          KNOW ALL MEN BY THESE  PRESENTS,  that  each  person  whose  signature
appears below  constitutes  and appoints C. Ray Holman and Roger A. Keller,  and
each of them severally,  his true and lawful  attorneys-in-fact and agents, with
full power of substitution  and  resubstitution,  for him and in his name, place
and stead, in any and all capacities,  to sign any and all amendments (including
post-effective amendments) to this Registration Statement, and to file the same,
with all exhibits thereto, and other documents in connection therewith, with the
Securities and Exchange  Commission,  granting unto said  attorneys-in-fact  and
agents,  and each of them,  full power and  authority to do and perform each and
every act and thing requisite or necessary to be done in and about the premises,
as fully to all intents and  purposes as he might or could do in person,  hereby
ratifying and confirming all that said attorneys-in-fact and agents or either of
them, or their or his substitute or substitutes,  may lawfully do or cause to be
done by virtue  hereof.  This Power of  Attorney  may be executed in one or more
counterparts.

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

/s/ C. Ray Holman                                 Chairman of the Board and
--------------------------------                  Chief Executive Officer
C. Ray Holman
Date:  August 18, 1999

/s/ Michael A. Rocca                              Senior Vice President and
--------------------------------                  Chief Financial Officer
Michael A. Rocca                                  (Principal Financial
Date:  August 18, 1999                            Officer)

/s/ Douglas A. McKinney                           Vice President and
--------------------------------                  Controller (Principal
Douglas A. McKinney                               Accounting Officer)
Date:  August 18, 1999

/s/ Raymond F. Bentele                            Director
--------------------------------
Raymond F. Bentele
Date:  August 18, 1999

/s/ Gareth C.C. Chang                             Director
--------------------------------
Gareth C.C. Chang
Date:  August 18, 1999

/s/ William L. Davis, III                         Director
--------------------------------
William L. Davis, III
Date:  August 18, 1999

/s/ Ronald G. Evens                               Director
--------------------------------
Ronald G. Evens
Date:  August 18, 1999

/s/ Roberta S. Karmel                             Director
--------------------------------
Roberta S. Karmel
Date:  August 18, 1999

/s/ Claudine B. Malone                            Director
--------------------------------
Claudine B. Malone
Date:  August 18, 1999

/s/ Anthony Viscusi                               Director
--------------------------------
Anthony Viscusi
Date:  August 18, 1999

/s/ Brian M. Rushton                              Director
--------------------------------
Brian M. Rushton
Date:  August 18, 1999

/s/ Daniel R. Toll                                Director
--------------------------------
Daniel R. Toll
Date:  August 18, 1999

          Pursuant  to the  requirements  of the  Securities  Act of  1933,  the
Employee   Benefits   Committee  of  Mallinckrodt  Inc.  has  duly  caused  this
Registration Statement to be signed on its behalf by the undersigned,  thereunto
duly authorized, in the City of St. Louis, State of Missouri, on the 18th day of
August, 1999.

                                              INVESTMENT PLAN FOR EMPLOYEES
                                                OF MALLINCKRODT INC.

                                              /s/ William B. Stone
                                              ----------------------------
                                              Name: William B. Stone
                                              Title: Chairman

                                POWER OF ATTORNEY

          KNOW ALL MEN BY THESE  PRESENTS,  that  each  person  whose  signature
appears below  constitutes  and appoints C. Ray Holman and Roger A. Keller,  and
each of them severally,  his true and lawful  attorneys-in-fact and agents, with
full power of substitution  and  resubstitution,  for him and in his name, place
and stead, in any and all capacities,  to sign any and all amendments (including
post-effective amendments) to this Registration Statement, and to file the same,
with all exhibits thereto, and other documents in connection therewith, with the
Securities and Exchange  Commission,  granting unto said  attorneys-in-fact  and
agents,  and each of them,  full power and  authority to do and perform each and
every act and thing requisite or necessary to be done in and about the premises,
as fully to all intents and  purposes as he might or could do in person,  hereby
ratifying and confirming all that said attorneys-in-fact and agents or either of
them, or their or his substitute or substitutes,  may lawfully do or cause to be
done by virtue  hereof.  This Power of  Attorney  may be executed in one or more
counterparts.

          Pursuant  to the  requirements  of the  Securities  Act of 1933,  this
Registration  Statement has been signed below by the following  persons in their
capacities  as  members  of the  Employee  Benefits  Committee  and on the  date
indicated.

        Signature                                        Date

/s/ Bruce K. Crockett                              August 18, 1999
----------------------------
Bruce K. Crockett

/s/ Roger A. Keller                                August 18, 1999
----------------------------
Roger A. Keller

/s/ David R. Kupferer                              August 18, 1999
----------------------------
David R. Kupferer

/s/ Judith C. Rebholz                              August 18, 1999
----------------------------
Judith C. Rebholz

/s/ John J. Riordan                                August 18, 1999
----------------------------
John J. Riordan

/s/ Nancy J. Stemme                                August 18, 1999
----------------------------
Nancy J. Stemme

/s/ William B. Stone                               August 18, 1999
----------------------------
William B. Stone

/s/ Frank A. Voltolina                             August 18, 1999
----------------------------
Frank A. Voltolina