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                                                                  Exhibit 10.35


September 10, 2001

PERSONAL AND CONFIDENTIAL

Mr. James R. Fitzgerald, Jr.
44 Blueberry Hill Lane
Sudbury, MA 01776

Dear Jim:

      We are pleased to offer you the full-time position of Senior Vice
President and Chief Financial Officer reporting to the Chief Executive Officer.
We are excited about the prospect of you joining our team, and look forward to
the addition of your professionalism and experience to help the Company achieve
its goals.

      Your salary will be paid at an initial rate of $17,500 per month, which
will be subject to annual review and adjustment, as solely determined by the
Company's Board of Directors. You will be paid in accordance with the Company's
normal payroll practices as established or modified from time to time.
Currently, salaries are paid on a semi-monthly basis.

      In addition to your base salary and at the discretion of the Board of
Directors, you will be eligible to receive each year a cash bonus of up to 25%
of your base salary based upon the following performance criteria, as set forth
by the Board of Directors: (i) 10% of base salary bonus if an unrestricted cash
and investment balance of at least $10 million dollars is maintained from
September 10, 2001 through December 31, 2002 and (ii) 15% of base salary bonus
provided you satisfactorily execute, as solely determined by the Board of
Directors, other fundraising responsibilities as mutually determined by you and
the CEO and Board of Directors. In order to be eligible to receive any bonus,
you must be employed through December 31 of the applicable bonus year. In
addition, and at the discretion of the Board of Directors, you will be eligible
for a prorated bonus for 2001 based on criteria that will be provided to you
hereafter.

      You will be eligible to participate in benefits programs to the same
extent as, and subject to the same terms, conditions and limitations applicable
to, other employees of the Company of similar rank and tenure. These benefits
currently include the Company's 401(k) Plan; medical, dental, term life, and
long-term disability insurance; partially subsidized parking of reimbursement of
up to $65.00 per month for a T-Pass. Your participation in these benefit plans
shall be subject to (i) the terms and conditions of the applicable plan
documents; (ii) generally applicable Company policies; and (iii) the discretion
of the Board or any administrative or other committee provided for in, or
contemplated by, each such plan. You will also be entitled to four weeks paid
vacation, which shall be accrued and utilized in accordance with the Company's
vacation
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                                     - 2 -

                                                                       ACUSPHERE


policy/practice as established and/or modified from time to time. Additionally,
the Company intends to obtain Directors and Officers Liability Insurance in
connection with its anticipated Initial Public Offering. You, along with the
Company's other officers and directors, also will be entitled to protection
under the indemnification provisions as set forth in the Company's By-Laws.

      Upon your hire, you will be granted the option to purchase 275,000 shares
of the Company's common stock, at an exercise price of $1.20 per share. In
addition, the Board of Directors will annually review potential additional
option grants as it does for all others on the management team. The options will
be subject to the terms and conditions of the Company's Incentive Stock Option
Agreement and Stock Option Plan, which will include, among other things, a
vesting schedule providing for vesting ratably over 48 months. In the event of
an Acquisition, as defined in paragraph 14(b) of the Incentive Stock Option
Agreement, 100% of your outstanding options shall accelerate and become
immediately exercisable. In the event of a sale, merger, or liquidation of all
or substantially all of the Company's assets prior to an Initial Public Offering
or December 31, 2002, whichever occurs first, and any such transaction is valued
at less than $85 million dollars such that the preferred stock does not convert
and no value accrues to your common stock, you may cancel any outstanding
options in exchange for a one-time lump sum payment of $315,000, notwithstanding
anything to the contrary in any stock option agreement. Your eligibility for
such lump sum payment is contingent on your being employed with the Company as
of the closing date of the sale, merger or liquidation. Said payment shall be
made within thirty days of your notice of exercise of the right to receive the
lump sum payment.

      Your employment with the Company is on an "at-will" basis, which means
that either you or the Company may terminate the employment relationship at any
time, for any or no reason, with or without Cause (as defined below), and with
or without prior notice. If the Company elects to terminate your employment for
Cause, you will be given thirty (30) days' written notice prior to such
termination or, at the Company's sole discretion, 30 days' pay in lieu of
notice. "Cause" for purposes of this Agreement shall mean: (i) dishonesty,
embezzlement, misappropriation of assets or property (tangible or intangible) of
the Company; (ii) gross negligence, breach of fiduciary duty to the Company,
theft or fraud; (iii) violation of federal or state securities laws: (iv) breach
of your Nondisclosure and Developments Agreement; (v) the commission of an act
that constitutes unfair competition with the Company or which induces any
customer or supplier to breach a contract with the Company; or (vi) the
commission of a felony, including a plea of guilty or nolo contendere.

      If your employment is terminated without Cause, you will be entitled to
salary continuation at your then current base salary for a period of six (6)
months from the termination date, to be paid in accordance with the Company's
payroll practice then in effect. If you elect to continue medical insurance
coverage during such six month period
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                                     - 3 -

                                                                       ACUSPHERE


in accordance with the provisions of the Consolidated Omnibus Reconciliation Act
of 1985 ("COBRA"), then the Company shall pay your monthly COBRA premium
payments as well as any dental insurance premiums for the period of salary
continuation payments or until you accept other employment, whichever occurs
first.

      Except as set forth in this or other applicable agreements, the Company
shall have no other obligations to you upon termination of employment other than
payment of any accrued but unused vacation.

      The Company requires you to verify that the performance of your position
at Acusphere does not and will not breach any agreement entered into by you
prior to employment with the Company (i.e., you have not entered into any
agreements with previous employers that are in conflict with your obligations to
Acusphere). Please provide us with a copy of any potentially conflicting
agreements for our review. You will also be required to sign the enclosed
Nondisclosure and Developments Agreement as a condition of your employment with
the Company. Additionally, for purposes of completing the INS I-9 form, please
provide the Company with sufficient documentation to demonstrate your
eligibility to work in the United States.

      Finally, we confirm that, provided that this letter agreement is executed
on September 10, 2001, and you begin full time employment with Acusphere on
September 10, 2001, we will pay your reasonable attorneys' fees in connection
with obtaining legal advice and assistance as to the review and/or negotiation
of this document, all related documents, and your employment by the Company, not
to exceed $5,000.

      We look forward to your joining Acusphere and starting with us on or
before September 10, 2001. We are confident that you will make a significant
contribution to our future success. We look forward to receiving a response from
you in writing by September 10, 2001 acknowledging that you have accepted this
offer of employment.

                                                   Sincerely,

                                                   /s/ Sherri C. Oberg
                                                   -----------------------------
                                                   Sherri c. Oberg
                                                   President and CEO

Accepted and Agreed to
As of this 10th day of September, 2001


/s/ James R. Fitzgerald
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