SecProbe.io

March 11, 2011

Dr. Michael Bristow President and Chief Executive Officer ARCA biopharma, Inc. 8001 Arista Place, Suite 200
Broomfield, Colorado 80021

Re: ARCA biopharma, Inc.
  Registration Statement on Form S-3
Filed March 9, 2011
  File No. 333-172686

Dear Dr. Bristow:
 We have limited our review of your registration statement to the filing of Part III
information prior to effectiveness.
 Please respond to this letter by amending your registration statement to include the
required Part III information or filing your definitive proxy statement prior to requesting acceleration of the registration statement.
 After reviewing any amendment to your re gistration statement and the information you
provide in response to this comment, we may have additional comments.
 We urge all persons who are responsible for th e accuracy and adequacy of the disclosure
in the filing to be certain that the filing incl udes the information the Securities Act of 1933 and
all applicable Securities Act rules require.  Since the company and its management are in
possession of all facts relating to a company’s disclosure, they are responsible for the accuracy and adequacy of the disclosures they have made.
Notwithstanding our comment, in the event you request acceleration of the effective date
of the pending registration statement please pr ovide a written statement from the company
acknowledging that:

• should the Commission or the staff, acting purs uant to delegated authority, declare the
filing effective, it does not foreclose the Co mmission from taking any action with respect
to the filing;

• the action of the Commission or the staff, acting pursuant to delegated authority, in
declaring the filing effective, does not relieve the company from its full responsibility for
the adequacy and accuracy of the disclosure in the filing; and

Michael Bristow ARCA biopharma, Inc. March 11, 2011 Page 2

• the company may not assert staff comments a nd the declaration of effectiveness as a
defense in any proceeding initiated by the Commission or any person under the federal securities laws of the United States.  Please refer to Rules 460 and 461 regarding re quests for acceleration.  We will consider a
written request for acceleration of  the effective date of the regi stration statement as confirmation
of the fact that those reques ting acceleration are aware of thei r respective responsibilities under
the Securities Act of 1933 and the Securities Excha nge Act of 1934 as they relate to the proposed
public offering of the securities specified in the above registration stat ement.  Please allow
adequate time for us to review any amendment prior to the requested effective date of the registration statement.
 Please contact Johnny Gharib at (202) 551- 3170 or me at (202) 551-3715 with any
questions.
Sincerely,
       Jeffrey Riedler
Assistant Director
 cc:  Brent D. Fassett, Esq.  Cooley LLP  380 Interlocken Crescent, Suite 900  Broomfield, Colorado 80021