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[logo] ROTH CAPITAL PARTNERS

                                                                    EXHIBIT 10.6

                               September 20, 2005

Mr. David B. Swank
Chief Financial Officer
Diomed Holdings, Inc.
One Dundee Park
P.O. Box 97 Andover, MA 01810

Dear David:

      Roth Capital Partners, LLC ("we," "us" or "RCP") is pleased to act as
financial advisor and co-placement agent for Diomed Holdings, Inc. ("you" or the
"Company") in connection with your proposed private placement. The terms of our
engagement are set forth below in this letter (this "Agreement"). We look
forward to working with you.

1.    The Offering.

                  (a) We currently anticipate raising approximately $10 million
       involving the sale in a private placement financing by the Company of
       equity or equity-linked securities (the "Offering") to institutional
       investors (the "Investors"). Of the approximately $10 million to be
       raised in the Offering, we anticipate that approximately $3 million will
       be sold to Investors introduced by RCP and with which RCP has substantial
       prior relationships, the names of which are listed on the attached
       Schedule A (the "RCP Investors"). The actual terms of the Offering will
       depend on market conditions, and will be subject to negotiation between
       the Company and prospective Investors.

                  (b) Although we cannot guarantee you that we will be able to
       raise new capital, we will conduct the offering on a "best efforts"
       basis.

                  (c) In turn, during the term of our engagement, you agree not
       to engage any other financial advisor, placement agent or finder to raise
       capital (including debt) for you except for Musket Research Associates,
       Inc. ("MRA").

                  (d) We will not approach any prospective Investor listed on
       Schedule A to the engagement letter between the Company and MRA.

                  (e) We will provide feedback to the Board of Directors of the
       Company with respect to our views as to the terms and conditions of the
       financing and how such terms and conditions compare with other
       transactions with which we are familiar in the current financing
       environment for companies comparable to the Company. The foregoing will
       not be a "fairness opinion" but rather will informal advice be provided
       to assist the Board of Directors in making its own determination, in the
       business judgment of the Board of Directors, of whether consummating the
       Offering is, or such Offering terms and conditions are, acceptable to the
       Company

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Diomed, Inc.
Page 2

      2.    Fees and Expenses.

                  (a) Contemporaneously with the consummation of the Offering,
      such that all of the funds to be raised in connection therewith have been
      paid to the Company (the "Proceeds"), the Company will pay us in cash a
      fee equal to five percent (5%) of the amount raised by us from RCP
      Investors. Such fee shall constitute the complete and full compensation
      payable to us and our agents arising from the Offering and the sale by the
      Company of securities thereunder to the Investors (including the RCP
      Investors and all other Investors), and neither the Company nor any of its
      agents, successors or assigns shall be entitled to any additional payment
      whatsoever hereunder, including in the event that the Company enters into
      any subsequent financing transaction of any nature with any one or more of
      the Investors (including the RCP Investors and all other Investors) in the
      Offering.

      3.    Term of Engagement.

                  (a) The term of our engagement will be the later of thirty
      days commencing on the day this Agreement is signed by Company or upon the
      close of the Offering. However, either party may terminate our engagement
      at any time upon 5 days written notice to the other party. Upon
      termination, we will be entitled to collect all fees earned (if any)
      through the date of termination.

      4. Representations and Warranties.

                   (a) We hereby represent and warrant to the Company that RCP
      is a duly-licensed broker-dealer and has all requisite approvals, power,
      licenses and registrations as are required to provide its services to the
      Company as set forth herein.

                   (b) You agree that, in connection with the Offering, you will
      enter into subscription, registration rights and other customary
      agreements, and that your counsel will supply an opinion letter on the
      transaction, all of which will be in form and substance reasonably
      acceptable to, and addressed to, us and the Investors.

                  (c) You further agree that we may rely upon, and are a third
      party beneficiary of, the representations and warranties and applicable
      covenants, set forth in any agreements with Investors in the Offering.

5.    Diligence; Information.  In connection with RCP's activities on your
       behalf, you will furnish RCP with all financial and other information
       regarding the Company that RCP reasonably believes appropriate to its
       assignment (all such information so furnished by the Company, whether
       furnished before or after the date of this Agreement, being referred
       to herein as the "Information").  The Company will provide RCP with
       reasonable access to the officers, directors, employees, independent
       accountants, legal counsel and other advisors and consultants of the
       Company.  You recognize and agree that RCP (i) will use and rely
       primarily on the Information and information available from generally
       recognized public sources in performing the services contemplated by
       this Agreement without independently verifying the Information or such
       other information, (ii) does not assume responsibility for the
       accuracy of the Information or such other information, and (iii) will
       not make an appraisal of any assets or liabilities owned or controlled
       by the Company or its market competitors.  We will maintain the
       confidentiality of the Information and, unless and until such
       information shall have been made publicly available by the Company or
       by others without breach of a confidentiality agreement, shall
       disclose the Information only as authorized by the Company or as
       required by law or by order of a governmental authority or court of
       competent jurisdiction.  If we are legally required to make disclosure
       of any of the Information, we will give notice to the Company prior to
       such disclosure, to the extent that we can practically do so.

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Diomed, Inc.
Page 3

      The foregoing paragraph shall not apply to information that:

(i)        at the time of disclosure by the Company is, or thereafter becomes,
           generally available to the public or within the industries in which
           the Company or its affiliates conduct business, other than as a
           direct result of a breach by us of our obligations under this
           Agreement;

(ii)       prior to or at the time of disclosure by the Company, was already in
           the possession of, or conceived by, us or any of our affiliates, or
           could have been developed by them from information then in their
           possession, by the application of other information or techniques in
           their possession, generally available to the public, or available to
           us or our affiliates other than from the Company (including as
           previously provided to us by the Company);

(iii)      at the time of disclosure by the Company or thereafter, is obtained
           by us or any of our affiliates from a third party who we reasonably
           believe to be in possession of the information not in violation of
           any contractual, legal or fiduciary obligation to the Company with
           respect to that information; or

(iv)       is independently developed by us or our affiliates.

      Nothing in this Agreement shall be construed to limit the ability of RCP
      or its affiliates to pursue, investigate, analyze, invest in, or engage in
      investment banking, financial advisory or any other business relationship
      with entities other than the Company, notwithstanding that such entities
      may be engaged in a business which is similar to or competitive with the
      business of the Company, and notwithstanding that such entities may have
      actual or potential operations, products, services, plans, ideas,
      customers or supplies similar or identical to the Company's, or may have
      been identified by the Company as potential merger or acquisition targets
      or potential candidates for some other business combination, cooperation
      or relationship. The Company expressly acknowledges and agrees that it
      does not claim any proprietary interest in the identity of any other
      entity in its industry or otherwise, and that the identity of any such
      entity is not confidential information.

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Diomed, Inc.
Page 4

6.     Indemnification and Contribution. The Company agrees to indemnify RCP and
       its controlling persons, representatives and agents in accordance with
       the indemnification provisions set forth in Appendix I, which is
       incorporated herein by this reference. These provisions will apply
       regardless of whether the proposed Offering is consummated or this
       Agreement is terminated.

7.    Other RCP Engagements.  Nothing in this Agreement shall be construed to
       limit the ability of RCP or its affiliates to pursue, investigate,
       analyze, invest in, or engage in investment banking, financial
       advisory or any other business relationship with entities other than
       the Company, notwithstanding that such entities may be engaged in a
       business which is similar to or competitive with the business of the
       Company, and notwithstanding that such entities may have actual or
       potential operations, products, services, plans, ideas, customers or
       supplies similar or identical to the Company's, or may have been
       identified by the Company as potential merger or acquisition targets
       or potential candidates for some other business combination,
       cooperation or relationship.  The Company expressly acknowledges and
       agrees that it does not claim any proprietary interest in the identity
       of any other entity in its industry or otherwise, and that the
       identity of any such entity is not confidential information.

8.     Other Finders and Placement Agents. You represent and warrant that, with
       the exception of MRA, there is no other person or entity that is entitled
       to a finder's fee or any type of brokerage commission in connection with
       the Offering as a result of any agreement or understanding with the
       Company.

9.    Governing Law.  This Agreement shall be governed by and construed in
       accordance with the laws of the State of New York applicable to
       contracts executed and to be wholly performed therein without giving
       effect to its conflicts of laws principles or rules.  The Company and
       MRA agree that any dispute concerning this Agreement shall be resolved
       through binding arbitration conducted by a panel of three arbitrators,
       one chosen by the Company, one chosen by MRA and the third chosen by
       the two arbitrators selected by the parties, pursuant to the
       commercial arbitration rules of the American Arbitration Association.
       If the parties are unable to reach agreement on the arbitration panel,
       the arbitrators will be appointed pursuant to the applicable
       commercial rules of the American Arbitration Association.  Arbitration
       will be venued in New York County, in the City and State of New York.

10.    Announcement of Offering. If the Offering is consummated, RCP may, at its
       expense, place an announcement in such newspapers and periodicals as RCP
       may desire, provided, that the Company shall have given its prior
       approval of each such announcement as to its content and form, such
       approval not to be unreasonably withheld.

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Diomed, Inc.
Page 5

11.   Advice to the Board.   The Company acknowledges that any advice given
       by us to you (including without limitation such advice as may be given
       pursuant to section 1(e) hereof) is solely for benefit and use of the
       Board of Directors of the Company and may not be used, reproduced,
       disseminated, quoted or referred to, without our prior written
       consent.  If disclosure of our advice is required by law or in your
       view is necessary for the defense of any proceeding, then,
       notwithstanding the foregoing, you may disclose such advice so long as
       you shall, prior to such disclosure, afford us the opportunity to
       review in advance the portion of such disclosure which mentions us or
       our advice and to approve the form thereof, such approval not to be
       unreasonably withheld by us.

12.    Entire Agreement. This Agreement (including any schedules and appendices
       hereto) constitutes the entire agreement between the parties and
       supersedes and cancels any and all prior or contemporaneous arrangements,
       understandings and agreements, written or oral, between them relating to
       the subject matter hereof.

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Diomed, Inc.
Page 6

      We look forward to working with you toward the successful conclusion of
this engagement, and developing a long-term relationship with the Company.

Very truly yours,

ROTH CAPITAL PARTNERS, LLC

By:
    --------------------------------------
      Christopher D. Jennings

      Managing Director

Confirmed and accepted as of
this ____ day of September, 2005:

DIOMED, INC.

By:
    --------------------------
      David B. Swank

      Chief Financial Officer

                     NOTE: SCHEDULES AND APPENDECES OMITTEDEXHIBIT 10.8

                          WAIVER OF NEGATIVE COVENANTS

The undersigned holder (the "Holder") of Variable Rate Convertible Debentures
due 2008 (the "Debentures") issued by Diomed Holdings, Inc. (the "Company") and
the Company hereby agree as follows:

In connection with the Company's proposed consummation of the purchase and sale
of the Company's Preferred Stock, par value $0.001 per share (the "Preferred
Stock") and Warrants (the "Investor Warrants") to purchase Common Stock, par
value $0.001 of the Company ("Common Stock"), for aggregate gross proceeds of
approximately $10,000,000 to $12,000,000, on substantially the terms and
conditions described in the term sheet annexed hereto as Exhibit A, and as the
Company and the investors in the Financing shall agree in the definitive
Financing documentation (the "Financing"), the Holder hereby waives the negative
covenants set forth in Sections 7(c) and 7(d) of the Debenture as they pertain
to the Financing. For the avoidance of doubt, the foregoing waiver pertains to
the Financing only and not to any future financing or other transaction which
would be precluded by the negative covenants contained in the Debenture. All
other terms and conditions of the Debenture remain in full force and effect.

Notwithstanding anything herein to the contrary, the waiver granted by the
Holder hereunder shall only apply to the extent that the Company redeems
securities for no more than the actual cash received for the original purchase
of such securities by the purchaser in the Financing. This waiver shall not
apply to the payment to any person or entity of any amounts above what was
initially paid for such securities, including but not limited to the payment of
any default premiums, liquidated damages or late fees. Any redemption above the
original purchase price paid by a participant in the Financing, in cash or kind,
shall remain strictly prohibited by the terms of the Debentures. Notwithstanding
anything herein to the contrary, the participants in the Financing shall be
permitted to collect customary liquidated damages after the effective date of
their registration statement for periods during which the prospectus thereunder
is not available for the resale of the shares held by such participants.

As an inducement to the Holder to provide the foregoing waiver, and in
consideration therefor, the Company hereby agrees to issue, effective at the
time of consummation of the Financing, to the Holder warrants to purchase an
aggregate of up to __________ shares of Common Stock (the "Debenture Holder
Warrants") on the same terms and conditions as the Investor Warrants. For the
avoidance of doubt, the Debenture Holder Warrants shall only be issuable if the
Company completes the Financing.

Dated:  September 26, 2005
                        [NAME OF HOLDER]

                        By:  ___________________________________
                                (Signature of authorized person above)

                        Name:  _________________________________
                        Title:    _________________________________

                        DIOMED HOLDINGS, INC.

                        By:  ___________________________________
                        David Swank, Chief Financial Officer

                                                       NOTE: EXHIBIT A OMITTED
                                                       ----

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