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April 11, 2005

Mail Stop 0306

Mr. Robert S. Breuil
Chief Financial Officer and Vice President of Corporate
Development
Aerogen, Inc.
2071 Stierlin Court, Suite 100
Mountain View, CA 94043

	Re:	Item 4.02 Form 8-K
		Filed March 9, 2005
		File No. 000-31913

Dear Breuil:

	We have reviewed your Item 4.02 Form 8-K for compliance with
the
form requirements and have the following comment.  Where
indicated,
we think you should revise your document in response to this
comment.
If you disagree, we will consider your explanation as to why our
comment is inapplicable or a revision is unnecessary.  After
reviewing this information, we may or may not raise additional
comments.

	Please understand that the purpose of our review process is
to
assist you in your compliance with the applicable disclosure
requirements and to enhance the overall disclosure in your filing.
We look forward to working with you in these respects.  We welcome
any questions you may have about our comments or on any other
aspect
of our review.  Feel free to call us at the telephone numbers
listed
at the end of this letter.

Form 8-K Filed March 9, 2005

1. We note that you intend to file restated financial statements.
However you have not indicated how or when you intend to do so.
Please tell us how and when you intend to file restated financial
statements. We may have further comment after you file the
restated
financial statements.

*    *    *    *

	Please file your supplemental response and amendment via
EDGAR
in response to this comment within five business days after the
date
of this letter.

      We urge all persons who are responsible for the accuracy and
adequacy of the disclosure in the filings reviewed by the staff to
be
certain that they have provided all information investors require
for
an informed decision.  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.

	In connection with responding to our comments, please
provide,
in writing, a statement from the company acknowledging that:

* the company is responsible for the adequacy and accuracy of the
disclosure in the filing;
* staff comments or changes to disclosures in response to staff
comments in the filings reviewed by the staff do not foreclose the
Commission from taking any action with respect to the filing; and
* the company may not assert staff comments as a defense in any
proceeding initiated by the Commission or any person under the
federal securities laws of the United States.

	In addition, please be advised that the Division of
Enforcement
has access to all information you provide to the staff of the
Division of Corporation Finance in connection with our review of
your
filing or in response to our comments on your filing.

	If you have any questions, please call me at (202) 824-5264.
In
my absence, you may call Brian Cascio, Branch Chief at (202) 942-
1791.

							Sincerely,

							Lynn Dicker
							Staff Accountant
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Mr. Robert S. Breuil
Aerogen, Inc.
April 11, 2005
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