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                                                                   EXHIBIT 10.25

                              SECOND SIDE AGREEMENT

This Second Side Agreement ("Second Side Agreement"), retroactively effective as
of the 30th day of September, 2000 ("Second Side Agreement Effective Date"), is
by and between ACLARA BIOSCIENCES, INC., located at 1288 Pear Avenue, Mountain
View, California, 94043 ("Aclara") and PE CORPORATION (NY), having its Applied
Biosytems Group located at 850 Lincoln Center Drive, Foster City, California
94404 ("ABG"). Aclara and ABG will be referred to collectively as the "Parties."

                                   BACKGROUND

A.       Prior to this Second Side Agreement, Aclara and ABG have entered into
         five agreements relating to the development and commercialization of
         microfluidic technology in the field of High Throughput Screening:

         1. a Collaboration Agreement having an effective date of April 25, 1998
              (the "GA Agreement");

         2. a Custom Instrument Development And Commercialization Agreement
              having an effective date of October 1, 1998 (the "PRI
              Agreement");

         3. a Collaboration Agreement having an effective date of March 19, 1999
              (the "HTS Agreement");

         4. a Side Agreement having an effective date of March 19, 1999 (the
              "PRI Side Agreement"); and

         5. an Amendment To Collaboration Agreement having an effective date of
               March 20, 2001 (the "Caliper Amendment").

B.       The Parties wish to modify their contractual relations in the field of
         High Throughput Screening in order to facilitate Aclara's independent
         development of certain instrument systems and microfluidic devices.

NOW, THEREFORE, in consideration of the foregoing premises and the mutual
promises and covenants contained herein and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
Parties, intending to be legally bound, do hereby agree as follows:

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                                    AGREEMENT

1.       NEW DEFINITIONS

1.1      DEFINITIONS. Any words with initial capitalization that are used in
         this Second Side Agreement that are not otherwise defined in this
         Second Side Agreement will have the meanings set forth in the HTS
         Agreement.

1.2      "Affiliates" has the meaning set forth at Section 1.1 of the HTS
         Agreement.

1.3      "Collaboration ACLARA Intellectual Property" has the meaning set forth
         at Section 1.4 of the HTS Agreement.

1.4      "Collaboration Field" has the meaning set forth at Section 1.20 of the
         HTS Agreement.

1.5      "Collaboration PERKIN-ELMER Intellectual Property" has the meaning set
         forth at Section 1.6 of the HTS Agreement.

1.6      "Exclusive Period" has the meaning set forth at Section 1.8 of the HTS
         Agreement.

1.7      "Existing Agreements" means the GA Agreement, the HTS Agreement, the
         PRI Agreement, the PRI Side Agreement, and the Caliper Amendment.

1.8      "High Throughput Screening" has the meaning set forth at Section 1.17
         of the HTS Agreement.

1.9      "Microfluidic Electrophoresis Device" has the meaning set forth at
         Section 1.21 of the HTS Agreement.

1.10     "Post Exclusive Period Product" means any Collaboration Product that is
         developed by Aclara or Aclara's Affiliate or licensee independently
         from ABG after the expiration of the Exclusive Period.

1.11     "Pre-Collaboration ACLARA Intellectual Property" has the meaning set
         forth at Section 1.3 of the HTS Agreement.

1.12     "PRI" means The R.W. Johnson Pharmaceutical Research Institute, a
         Division of Ortho-McNeil Pharmaceutical, Inc.

1.13     "Subject Patents" has the meaning set forth at Section 1.13 of the HTS
         Agreement.

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2.       ACCELERATION OF THE EXCLUSIVE PERIOD

The Parties agree to alter the term of the Exclusive Period such that the
Exclusive Period will end upon the Second Side Agreement Effective Date. As
such, existing Section 1.8 of the HTS Agreement is hereby deleted and replaced
by the following:

         1.8      "Exclusive Period" means the term beginning on the Effective
                  Date and ending upon the Second Side Agreement Effective Date.

3.       REALLOCATION OF RESPONSIBILITIES

Certain responsibilities of the Parties with respect to the commercialization of
Post Exclusive Period Product are hereby clarified or altered from those set
forth in the HTS Agreement as follows:

(A)      for the sake of clarity, the Parties agree that the development and
         commercialization of the Post Exclusive Period Product will be excluded
         from the exclusivity provisions of Sections 3.2.1 and 3.3.1 of the HTS
         Agreement;

(B)      ABG grants to Aclara and its Affiliates a non-exclusive license, with
         the right to license third parties  through the sale of Post  Exclusive
         Period  Product or for the  purpose of  manufacture  of Post  Exclusive
         Period  Product,  under  Valid  Claims of Subject  Patents  which claim
         Collaboration   PERKIN-ELMER   Intellectual   Property  as   reasonably
         necessary to effect the use,  development and  commercialization of the
         Post  Exclusive   Period  Product  by  Aclara  and  its  Affiliates  or
         licensees,  as such non-exclusive license is set forth at Section 5.4.5
         of the HTS Agreement,  provided,  however,  any royalties  shall be due
         only with respect to Post Exclusive Period Product that is covered by a
         Valid Claim of a Subject Patent which claims Collaboration PERKIN-ELMER
         Intellectual Property;

(C)      ABG grants to Aclara and its Affiliates a non-exclusive, royalty-free
         license, with the right to license third parties, under Valid Claims of
         Subject Patents which claim Collaboration Joint Intellectual Property
         as necessary or useful to effect the use, development and
         commercialization of the Post Exclusive Period Product by Aclara and
         its Affiliates or licensees;

(D)      for the sake of clarity, nothing in this Second Side Agreement will
         restrict the rights of Aclara nor require Aclara to pay royalties with
         respect to claims of Subject Patents which claim Pre-Collaboration
         ACLARA Intellectual Property or Collaboration ACLARA Intellectual

         Property;

(E)      for the sake of clarity, the Parties agree that notwithstanding Section
         3.2.2 of the HTS Agreement, Aclara will be responsible for all expenses
         relating to the marketing, sales, and support of the Post Exclusive
         Period Product; and

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(F)      notwithstanding Section 3.2.3 of the HTS Agreement, the Post Exclusive
         Period Product developed by Aclara will be marked so as to indicate
         that such product is a product of Aclara and/or its Affiliate or
         licensee alone, and not a product of ABG.

4.       PRI AGREEMENT

4.1      PAYMENTS FROM PRI. The Parties agree that any and all future payments
         by PRI under the PRI Agreement (including, without limitation, all
         payments that were accrued under Article 6 of the HTS agreement prior
         to or after the Second Side Agreement Effective Date but have not yet
         been paid by PRI) may, in Aclara's discretion, be made by PRI directly
         and solely to Aclara.

4.2      RIGHTS AND OBLIGATIONS. The Parties agree that, concurrently with this
         Second Side Agreement, the PRI Agreement will be separately amended in
         writing by the Parties and PRI such that (A) as an express condition to
         ABG's obligations under this Article 4, PRI shall grant to ABG a
         release in writing of all future obligations to PRI under the PRI
         Agreement except for ABG's confidentiality obligations thereunder and
         all such released obligations will be assumed solely by ACLARA, and (B)
         the PRI Agreement shall be amended with respect to ABG as of the Second
         Side Agreement Effective Date and all future rights of ABG under the
         PRI Agreement will accrue solely to Aclara.

5.       NO LICENSES

No license other than the licenses expressly set forth at Section 3(B) and 3(C)
of this Second Side Agreement is granted hereunder, whether express, implied, or
by estoppel, to any patent rights, or any other intellectual property rights,
owned, used, licensed to, or otherwise controlled by, ABG.

6.       CONTINUED FORCE AND EFFECT OF EXISTING AGREEMENTS

All provisions of the Existing Agreements, except as modified by this Second
Side Agreement, will remain in full force and effect and are hereby reaffirmed.
Other than as expressly stated in this Second Side Agreement, this Second Side
Agreement will not operate as a waiver of any condition or obligation imposed on
the Parties under the Existing Agreements.

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7.       INTERPRETATION OF SECOND SIDE AGREEMENT

In the event of any conflict, inconsistency, or incongruity between any
provision of this Second Side Agreement and any provision of the Existing
Agreements, the provisions of this Second Side Agreement will govern and
control.

8.       ASSIGNABILITY

This Second Side Agreement and the licenses herein granted will be binding upon
and inure to the benefit of the successors in interest of the respective
Parties. Neither Party has the power to assign this Agreement nor any interest
hereunder without the written consent of the other Party; provided, however,
that either Party may assign this Agreement or any of its rights or obligations
to any Affiliate or to any third party with which it may merge or consolidate,
or to which it may transfer all or substantially all of its assets to which this
Agreement relates, without obtaining the consent of the other Party, subject to
such Affiliate or third party assuming all liabilities and obligations under
this Second Side Agreement.

9.       ENTIRE AGREEMENT

This Second Side Agreement, along with the Existing Agreements, constitute the
sole agreements between the Parties relating to the subject matter hereof and
supersede all previous writings and understandings. Neither Party has been
induced to enter into this Second Side Agreement by, nor is any Party relying
on, any representation or warranty outside those expressly set forth in this
Second Side Agreement.

10.      COUNTERPARTS

This Second Side Agreement may be executed in any number of counterparts, and
each counterpart will be deemed an original instrument, but all counterparts
together will constitute one agreement.

[Signature page follows.]

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The Parties, through their authorized officers, have executed this Second Side
Agreement as of the Second Side Agreement Effective Date.

ACLARA BIOSCIENCES, INC.                 PE CORPORATION (NY), THROUGH
                                         ITS APPLIED BIOSYSTEMS GROUP

By:    /s/ Joseph M. Limber              By:    /s/ Michael W. Hunkapiller

Name:  Joseph M. Limber                  Name:  Michael W. Hunkapiller

Title: President and Chief Executive     Title: President Applied Biosystems
                                                Group, Executive Vice President,
                                                PE Corporation (NY)

Date:  October 15, 2001                  Date:  October 8, 2001
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