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                                                                    EXHIBIT 10.5

                                  VIACELL INC.

August 1, 2005

Anne Marie Cook
78 Walnut Street
Braintree, MA  02184

Dear Anne Marie,

On behalf of ViaCell, Inc. (the "Company"), I am pleased to extend an offer of
employment to you. You have made an outstanding impression throughout the
interview process, and we feel confident that you will become a valuable asset
to the company. Information about ViaCell as well as the details of our offer of
employment are summarized below.

VIACELL MISSION     To provide the highest quality cellular medicines for the
                    treatment of human diseases.

VIACELL CULTURE     We are dedicated to delivering revolutionary medicines
                    through development of important new therapeutic
                    applications. Every day you will be contributing to a
                    technology that is enriching of the lives of people in the
                    future. We hire innovative thinkers, with the skills and
                    capabilities to thrive on a high quality, success driven
                    team.

POSITION            General Counsel and Senior Vice President of Legal reporting
                    to Marc Beer, Chief Executive Officer. This position is a
                    key factor in ViaCell's continued success, and I am
                    confident that it will be an exciting opportunity for you as
                    well.

COMPENSATION        The starting base salary for this position for the 2005
                    fiscal year will be $280,000 per year payable in bi-weekly
                    installments of $10,769.23. For the 2005 fiscal year and
                    thereafter, this base salary shall be subject to adjustment.
                    Currently our standard annual salary review process occurs
                    each January for senior management.

                    In addition, you will be eligible to participate in the
                    Management Bonus Plan at an annual target of 35% of your
                    base salary, payable annually based on agreed to company and
                    individual performance objectives. Eligibility will begin on
                    your start date and will be prorated for 2005. Your bonus
                    payout is determined based on achievement of both corporate
                    and individual goals.

STOCK OPTIONS       As an incentive for you to participate in the Company's
                    future growth, you will receive, subject to approval by our
                    Board of Directors, options to purchase up to 75,000 shares
                    of our Common Stock (the "Options"). The Options will be
                    incentive stock options ("ISO's") to the extent allowable
                    under the Internal

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Anne Marie Cook
August 1, 2005
Page 2

                    Revenue Code. The exercise price of the Options equals the
                    fair market value of our Common Stock as determined by the
                    Board of Directors on the date of grant approval. The
                    Options will vest quarterly over four years beginning on the
                    last day of the first quarter after the date of commencement
                    of your employment. The Options will be granted under the
                    Company's 1998 Equity Incentive Plan pursuant to an ISO
                    certificate or non statutory stock option ("NSO")
                    certificate, as appropriate, shall have a term of ten years
                    and contain such additional terms as shall be determined by
                    the Board of Directors of the Company or the Compensation
                    Committee thereof.

ADDITIONAL          ViaCell will provide for twelve (12) months' severance pay
EMPLOYMENT          in the event of involuntary termination without cause or
TERMS               voluntary termination for good reason. If the Company shall
                    terminate your employment without "cause" or if you
                    terminate your employment for "good reason," then ViaCell
                    will continue paying your base salary and medical and dental
                    benefit contributions for a period of twelve (12) months in
                    accordance with its regular payroll practices at such time.
                    The term "cause" as used here means (i) your continued
                    failure to substantially perform your duties provided you
                    are reasonably notified of such failure and given reasonable
                    time to correct such failure, (ii) any misappropriation of
                    funds, properties or assets of the Company by you, (iii) any
                    damage or destruction of any property or assets of the
                    Company caused by you, whether resulting from your willful
                    actions or willful omissions or gross negligence; (iv) your
                    being convicted of a felony; or (v) any material breach of
                    your employment obligations or of the Intellectual Property
                    and Confidential Information Agreement. The term "good
                    reason" as used here means any action by the Company without
                    your prior consent which results in (i) any material
                    diminution in your title, position, duties, responsibilities
                    or authority; or (ii) any breach by the Company of any
                    material provision contained herein.
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Anne Marie Cook
August 1, 2005
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CHANGE OF CONTROL   Upon a Change of Control with the Company, if the company
                    terminates your employment without "cause" within twelve
                    months of the change in control or you voluntarily resign
                    for "good reason", all options granted as of that date shall
                    become fully vested and exercisable and ViaCell will
                    continue paying your base salary and benefits for a period
                    of twelve (12) months following the date of termination. The
                    options will continue to be subject to the grant provisions
                    under the 1998 Plan. A "Change in Control" shall mean: (i) a
                    merger, consolidation or similar combination after which 50%
                    or more of the voting stock of the surviving corporation is
                    held by persons who were not stockholders of the Company
                    immediately prior to such merger or combination; (ii) the
                    sale, transfer or other disposition of all or substantially
                    all of the Company's assets to one or more persons (other
                    than any wholly owned subsidiary of the Company) in a single
                    transaction or series of related transactions; or (iii) any
                    person or related group of persons (other than the Company
                    or a person that directly or indirectly controls, is
                    controlled by, or is under common control with the Company)
                    directly or indirectly acquires beneficial ownership
                    (determined pursuant to Rule 13d-3 promulgated under the
                    Securities Exchange Act of 1934, as amended) of securities
                    possessing more than 50% of the total combined voting power
                    of the Company's outstanding securities pursuant to a tender
                    or exchange offer made directly to the Company 's
                    stockholders.

BENEFITS            Because we care about the well being of our employees, we
                    are pleased to provide you with a comprehensive offering of
                    benefits. Our benefits currently include medical, dental,
                    life insurance, 401k, three weeks vacation (accrued monthly
                    and pro-rated during your first calendar year of
                    employment), balance benefit, educational assistance and
                    flexible-spending accounts. Additional information about
                    these benefits is outlined in the enclosed summary.

                    You will be entitled to an additional two weeks of vacation
                    beyond our standard benefit package.

ELIGIBILITY FOR     The Immigration Reform and Control Act of 1986 requires
EMPLOYMENT          ViaCell to review documentary evidence that you are eligible
                    for employment. This requirement applies to US citizens, as
                    well as foreign nationals. A list of approved documents that
                    are acceptable as verification of employment eligibility are
                    listed on page two of the I-9 form which will be included
                    with your orientation packet. Please bring the appropriate
                    documents with you on your first day of employment.

EMPLOYMENT          While we look forward to a long and mutually beneficial
RELATIONSHIP        relationship, you acknowledge that this letter does not
                    constitute a contract of employment for any particular
                    period of time and does not affect the at-will nature of the
                    employment relationship with the company. Either you or
                    ViaCell have the right to terminate your employment at any
                    time.

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Anne Marie Cook
August 1, 2005
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We are very excited about the future of ViaCell and believe that the
opportunities presented will allow you significant personal and professional
growth. If you have any questions or concerns, please do not hesitate to contact
me anytime. We look forward to having you join our team!

Sincerely,

/s/ Marc D. Beer
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Marc Beer
Chief Executive Officer

Please acknowledge your acceptance of this offer by signing a copy of this
document along with the Agreement Related to Intellectual Property and
Confidential Information and Code of Ethics, and faxing all to Kathleen Hayes at
617-577-9045. This offer will remain in effect for a period of seven (7)
calendar days from the date of this letter.

/s/ Anne Marie Cook                    August 2, 2005
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Signature                              Date