Exhibit 10.5 to 8-K

                             [Letterhead of Diomed]

                                February 15, 2005

Mr. John Welch
c/o Diomed Holdings, Inc.
One Dundee Park
Andover, MA 01810

Dear John:

This letter refers to the letter agreement (the "Letter Agreement"), dated
September 9, 2002, between you and Diomed, Inc. (the "Company"). After
consideration by the Compensation Committee of the Board of Directors of Diomed
Holdings, Inc., the Company has determined to extend to you a right to receive
severance pay that may become payable under certain circumstance set forth below
in this letter.

Subject to your acceptance of the following terms and conditions, the Company
proposes to amend the Letter Agreement by deleting the existing Section 6 and by
adding the following provision in lieu thereof:

         "6. You will be an at-will employee. The terms of your employment will
         be interpreted in accordance with and governed by the laws of The
         Commonwealth of Massachusetts. If the Company terminates your
         employment without Cause (as defined below in this Section), you shall
         be entitled to receive as severance an amount equal to twelve (12)
         months of your annual base salary at the time in effect payable in a
         single lump sum payable within ten (10) business days of the date on
         which you receive notice of termination of employment; provided, that
         the Company shall have no obligation to make any severance payment to
         you (i) unless and until you execute and deliver to the Company, and do
         not revoke, a release of all claims (other than for amounts owed him
         hereunder) in form and substance satisfactory to the Company, including
         the Company's satisfaction that such release complies with the
         requirements of the Age Discrimination in Employment Act, or (ii) if
         you breach your obligation not to compete with the Company or not to
         divulge confidential information of the Company as set forth in your
         separate agreement with the Company containing such obligations. If you
         voluntarily terminate your employment, you shall be entitled to receive
         your base salary accrued through the date of termination. For all
         purposes of the Letter Agreement, "Cause" shall mean: (i) your
         embezzlement, willful breach of fiduciary duty or fraud with regard to
         the Company or any of the Company's assets or businesses; (ii) your
         conviction of, or pleading of nolo contendre with regard to, a felony
         (other than a traffic violation) or any other crime involving moral
         turpitude and involving any activity or activities related to the
         affairs of the Company; or (iii) any other breach by you of a material
         provision of the terms of your employment hereunder that remains
         uncured for thirty (30) days after written notice thereof is given to
         you. If the Company terminates your employment for Cause, the Company
         shall have no further obligation or liability to you relating to your
         employment hereunder, or the termination thereof, other than for your
         base salary earned but unpaid through the date of termination. "

Except as expressly set forth herein, the Letter Agreement will remain in full
force and effect without further amendment of any other provision thereof.

To indicate your agreement with the foregoing, please sign in the space provided
below and return an original executed counterpart to me, whereupon the Letter
Agreement, as amended hereby, will be a binding and enforceable agreement
between you and the Company.

                                          Very truly yours,

                                          /s/  James A. Wylie, Jr.
                                          -------------------------------------
                                          James A. Wylie, Jr.
                                          President and Chief Executive Officer

Accepted and agreed to:

  /s/  John Welch
  ----------------------
  John Welch