EXHIBIT 10.37

                             SECOND LEASE AMENDMENT

     This SECOND LEASE AMENDMENT (the "Second Amendment") is executed as of this
31st day of December,  1998, by and between DUKE REALTY LIMITED PARTNERSHIP,  an
Indiana limited  partnership,  by and through its general  partner,  Duke Realty
Investments,  Inc., an Indiana corporation,  authorized to do and doing business
in the State of  Missouri,  as  Landlord  (hereinafter  "Landlord")  and EXPRESS
SCRIPTS,  INC., a Delaware  corporation,  authorized to do and doing business in
the State of Missouri, as Tenant (hereinafter "Tenant").

                              W I T N E S S E T H:

     WHEREAS,  Landlord and Tenant  entered into a certain Office Lease dated as
of August 14, 1998 for all of the space in that certain  Building (as defined in
said  Office  Lease)  which  Landlord  is  in  the  process  of  causing  to  be
constructed,  which said Office  Lease was  heretofore  amended by that  certain
First Lease Amendment dated as of November 5, 1998 (the "First  Amendment") (the
said  Office  Lease  and the  First  Amendment  being  hereinafter  referred  to
collectively as the "Lease"); and

     WHEREAS,  Landlord  and  Tenant  desire to  further  amend the Lease in the
limited respects hereinafter set forth.

     NOW,  THEREFORE,  in  consideration  of the premises,  the mutual covenants
herein contained and each act performed  hereunder by the parties,  Landlord and
Tenant hereby agree as follows:

     1. Except as otherwise  herein  specifically  provided,  terms used in this
Second Lease Amendment shall have the meaning set forth in the Lease.

     2. At the  beginning of the second and third  paragraphs  of Section  3.11,
INSURANCE,  the word "Landlord"  shall be substituted for the word "Tenant".  In
the tenth (10th) line of the second  paragraph of Section 3.11,  INSURANCE,  the
word "Landlord" shall be substituted for the word "Tenant". The last sentence of
the  second  paragraph  of  Section  3.11,  INSURANCE,  shall be  deleted in its
entirety. At the end of the fourth paragraph of Section 3.11, INSURANCE,  before
the  period  the words  "and  Tenant"  shall be  added.  At the end of the fifth
paragraph of Section 3.11, INSURANCE, the word "Tenant" shall be substituted for
the word "Landlord".  At the beginning of the first and third lines of the sixth
paragraph of Section 3.11,  INSURANCE,  the word "Landlord" shall be substituted
for the word "Tenant".  At the end of Section 3.11, INSURANCE shall be added the
following:  "The reasonable cost of insurance required by the provisions of this
Section  3.11,  INSURANCE to be provided by Landlord  shall be paid by Tenant to
Landlord  within  thirty  (30) days of  receipt  by Tenant  of a  statement,  in
reasonable detail, as Additional Rent."

     3. This Second  Amendment shall be incorporated  into and made apart of the
Lease.  All  provisions  of the Lease not expressly  modified or amended  hereby
shall remain in full force and effect.

     IN WITNESS WHEREOF,  the parties have caused this Second Lease Amendment to
be executed as of the day and year first written above.

LANDLORD:                             DUKE REALTY LIMITED PARTNERSHIP,
                                      an Indiana limited partnership

                                      By:    DUKE REALTY INVESTMENTS, INC.
                                             an Indiana corporation,
(SEAL)                                       its general partner


                                             By: /s/ Gregory Thurman
ATTEST:                                      W. Gregory Thurman
                                             Vice President and General Manager,
/s/ James D. Echkoff                         St. Louis Office Group
James D. Eckhoff
Vice President
and Corporate Attorney


TENANT:                                EXPRESS SCRIPTS, INC.,
                                       a Delaware corporation


(SEAL)                                  By:  /s/ Barrett Toan
                                             Barrett Toan, President

ATTEST:

/s/ Thomas M. Boudreau
Thomas M. Boudreau
Secretary


STATE OF MISSOURI   )
                    )  SS.
COUNTY OF ST. LOUIS )


     On this 12th day of February 1999, before me personally appeared W. GREGORY
THURMAN, to me personally known, who, being by me duly sworn, did say that he is
Vice  President  and General  Manager,  St.  Louis  Office  Group of DUKE REALTY
LIMITED PARTNERSHIP, an Indiana limited partnership, and general partner in DUKE
REALTY INVESTMENTS,  INC., an Indiana corporation,  and that the seal affixed to
the foregoing SECOND LEASE AMENDMENT is the corporate seal of said  corporation,
and that said  SECOND  LEASE  AMENDMENT  was signed and sealed on behalf of said
limited  partnership  and  said  corporation,  by  authority  of  its  Board  of
Directors,  and said W. GREGORY Thurman acknowledged said SECOND LEASE AMENDMENT
to be  the  free  act  and  deed  of  the  said  limited  partnership  and  said
corporation.

     IN WITNESS  WHEREOF,  I have  hereunto  set my hand and affixed my official
seal in the County and State aforesaid, the day and year first above written.


                                        /s/ Kathleen M. Wade
                                             Notary Public


STATE OF MISSOURI   )
                    ) SS.
COUNTY OF ST. LOUIS )


     On this 25th day of January  1999,  before me appeared  BARRETT TOAN, to me
personally  known, who, being by my duly sworn, did say that he is the President
of EXPRESS SCRIPTS,  INC., a corporation of the State of Delaware,  and that the
seal  affixed  to  the  foregoing  instrument  is the  corporate  seal  of  said
corporation,  and that said  instrument  was signed and sealed on behalf of said
corporation  by  authority  of its Board of  Directors;  and said  BARRETT  TOAN
acknowledged said instrument to be the free act and deed of said corporation.

     IN WITNESS  WHEREOF,  I have  hereunto  set my hand and affixed my official
seal in the County and State aforesaid, the day and year first above written.


                                             /s/ Kathleen M. Dolan
                                                 Notary Public