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                                                                       Exhibit 5

                               Hale and Dorr LLP
                              Counsellors At Law
                 60 State Street, Boston, Massachusetts 02109
                        617-526-6000 * FAX 617-526-5000

                                    December 21, 1999

Cambridge Heart, Inc.
1 Oak Park Drive
Bedford, MA  01730

     Re:  Registration Statement on Form S-8
          ----------------------------------

Ladies and Gentlemen:

     This opinion is furnished to you in connection with a Registration
Statement on Form S-8 (the "Registration Statement") filed with the Securities
and Exchange Commission (the "Commission") under the Securities Act of 1933, as
amended (the "Securities Act"), for the registration of 300,000 shares of Common
Stock, $.001 par value per share (the "Shares"), of Cambridge Heart, Inc., a
Delaware corporation (the "Company"), issuable upon the exercise of options
granted under the Company's 1996 Equity Incentive Plan (the "1996 Incentive
Plan").

     In this connection, we have examined signed copies of the Registration
Statement as filed with the Commission.  We have also examined and relied upon
the 1996 Incentive Plan, minutes of meetings of the stockholders and the Board
of Directors of the Company as provided to us by the Company, record books of
the Company as provided to us by the Company, the Certificate of Incorporation
and By-Laws of the Company, each as restated and/or amended to date, and such
other documents as we have deemed necessary for purposes of rendering the
opinions hereinafter set forth.

     In our examination of the foregoing documents, we have assumed the
genuineness of all signatures, the authenticity of all documents submitted to us
as originals, the conformity to original documents of all documents submitted to
us as copies, the authenticity of the originals of such latter documents and the
legal competence of all signatories to such documents.

     We express no opinion herein as to the laws of any state or jurisdiction
other than the state laws of the Commonwealth of Massachusetts, the Delaware
General Corporation Law statute and the federal laws of the United States of
America.  To the extent that any other laws govern the matters as to which we
are opining herein, we have assumed that such laws are identical to the state
laws of the Commonwealth of Massachusetts, and we are expressing no opinion
herein as to whether such assumption is reasonable or correct.

     Based upon and subject to the foregoing, we are of the opinion that the
Shares have been duly authorized for issuance and, when such Shares are issued
and paid for in accordance with the terms of

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Cambridge Heart, Inc.
December 21, 1999
Page 2


the 1996 Incentive Plan as contemplated by the Registration Statement, such
Shares will be validly issued, fully paid and nonassessable.

     Please note that we are opining only as to the matters expressly set forth
herein, and no opinion should be inferred as to any other matters. This opinion
is based upon currently existing statutes, rules, regulations and judicial
decisions, and we disclaim any obligation to advise you of any change in any of
these sources of law or subsequent legal or factual developments which might
affect any matters or opinions set forth herein.

     We hereby consent to the filing of this opinion with the Commission as an
exhibit to the Registration Statement in accordance with the requirements of
Item 601(b)(5) of Regulation S-K under the Securities Act.  In giving such
consent, we do not hereby admit that we are in the category of persons whose
consent is required under Section 7 of the Securities Act or the rules and
regulations of the Commission.

                                    Very truly yours,

                                    /s/ Hale and Dorr LLP

                                    HALE AND DORR LLP