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                                                                    Exhibit 10.1


                         COMMON STOCK PURCHASE AGREEMENT

         This Common Stock Purchase Agreement (the "Agreement") is made as of
March 14, 2003 by and between_________________ ("Purchaser") and Dyax Corp.
("Company"), whereby the parties agree as follows:

         The Purchaser shall buy from the Company and the Company shall sell to
the Purchaser _____________ shares (the "Shares") of the Company's common stock,
par value $0.01 per share (the "Common Stock"), at a price of $1.86 per share
for an aggregate purchase price of $______________ (the "Purchase Price").

         The Shares are being issued and sold pursuant to a registration
statement on Form S-3, File No. 333-86904, which registration statement has been
declared effective by the Securities and Exchange Commission. The Company is
delivering herewith prior to funding a prospectus supplement dated March 14,
2003 on Form 424(b)(5), which includes the prospectus dated May 3, 2002
(together, the "Prospectus"), regarding the sale of the Shares, which electronic
delivery Purchaser acknowledges and accepts by signing below. The Shares are
free of restrictive legends and are free of any resale restrictions.

         The Prospectus does not contain any untrue statement of a material fact
or omit to state any material fact required to be stated therein or necessary to
make the statements therein not misleading, and the Prospectus, as amended or
supplemented, if applicable, at the closing date of the transaction contemplated
hereby, will not contain any untrue statement of a material fact or omit to
state a material fact necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading.

         Not later than March 19, 2003:

         1. The Purchaser shall deliver a check for the Purchase Price to the
attention of Steve Galliker at the Company or wire the Purchase Price to the
Company to the account set forth below.


DOMESTIC WIRE TRANSFER:                 INTERNATIONAL WIRE TRANSFER:
--------------------------------------------------------------------------------
Instruct the paying financial           Instruct the paying financial
institution or the payor to             institution or the payor
route all domestic wire transfers       financial institution or the payor
via FEDWIRE to the following            to the to route all international wire
ABA Number:                             transfers to Silicon Valley Bank:

TO:                 SIL VLY BK SJ       CREDIT:  SILICON VALLEY BANK
                                                 3003 TASMAN DRIVE
ROUTING & TRANSIT:  121140399                    SANTA CLARA, CA 95054, USA

FOR CREDIT OF:      DYAX CORP           ROUTING & TRANSIT #:   \\FW:121140399

CREDIT ACCOUNT #:   3300388449          SWIFT CODE:            SVBKUS6S

BY ORDER O      [NAME OF SENDER]        FOR CREDIT OF:   DYAX CORP

                                        FINAL CREDIT ACCOUNT #: FNC - 3300388449

                                        BY ORDER OF:   [NAME OF SENDER]

--------------------------------------------------------------------------------
                                  IMPORTANT!!!!

Wire instructions MUST designate your FULL TEN DIGIT ACCOUNT NUMBER. Wires
received by Silicon Valley Bank with INCOMPLETE or INVALID ACCOUNT NUMBERS MAY
BE DELAYED AND COULD POSSIBLY REQUIRE RETURN TO THE SENDING BANK DUE TO
NEW REGULATIONS.
--------------------------------------------------------------------------------

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         2. Unless instructed below to deliver share certificates or otherwise
instructed by the Purchaser in writing, upon receipt of the Purchase Price, the
Company shall cause its transfer agent to transmit the Shares electronically to
the Purchaser by crediting the account set forth below through the Deposit
Withdrawal Agent Commission system.

         Purchaser DWAC Instructions:
                                     ------------------------------------------
         DTC No.
                ---------------------------------------------------------------
         Account No.
                    -----------------------------------------------------------
         Account Name:
                      ---------------------------------------------------------

         FOR DELIVERY OF SHARE CERTIFICATES ONLY (instead of crediting an
account through the Deposit Withdrawal Agent Commission system), please complete
the following:

         Account Name(s):
                         ------------------------------------------------------
         Account Address:
                         ------------------------------------------------------
         Contact Person:
                        -------------------------------------------------------
         Telephone:
                   ------------------------------------------------------------
         Facsimile:
                   ------------------------------------------------------------

         3. Notices to the Company shall be delivered to:

         Dyax Corp.
         300 Technology Square
         Cambridge, MA 02139
         Attn:  Henry E. Blair, President and Chief Executive Officer
         Facsimile Telephone:  (617) 374-3773

         4. Delivery of an executed copy of a signature page to this Agreement
by facsimile transmission shall be effective as delivery of a manually executed
copy of this Agreement and shall be effective and enforceable as the original.
This Agreement shall be governed and construed in accordance with the internal
laws of the Commonwealth of Massachusetts without giving effect to the conflicts
of law principles thereunder.

AGREED AND ACCEPTED, as of the date indicated above:

                                   DYAX CORP.

                                   By:
                                      -----------------------------------------
                                      Henry Blair
                                      President and Chief Executive Officer


                                                                               2

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                                      Purchaser Name:

                                      -----------------------------------------
                                      [Name]

                                      By:
                                         --------------------------------------
                                      Name:
                                           ------------------------------------
                                      Title:
                                            -----------------------------------
                                      Address for Notice:
                                                         ----------------------

                                                         ----------------------

                                                         ----------------------


                                                                               3


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                                   SCHEDULE 1

      PURCHASER                      NUMBER OF SHARES   AGGREGATE PURCHASE PRICE
      ---------                      ----------------   ------------------------
American Skandia Trust
Fed Aggressive Growth                     187,300              $348,378.00
Federated Kaufmann Fund                 1,148,269            $2,135,780.34
Federated Kaufmann Small Cap Fund          66,700              $124,062.00
Lancet Capital Health Ventures, L.P.    1,344,087            $2,500,001.82
Loeb Partners Corporation Agent         1,075,269            $2,000,000.34
Margrit Kelly                             400,000              $744,000.00
Francis and Margrit Kelly                 500,000              $930,000.00
                                     -------------------------------------------
Total:                                  4,721,625            $8,782,222,50