EXHIBIT 5.1

                             WHITE & MCDERMOTT, P.C.
                                65 WILLIAM STREET
                               WELLESLEY, MA 02481


                                November 1, 2001

Advanced Magnetics, Inc.
61 Mooney Street
Cambridge, Massachusetts  02138

      Re: 1993 STOCK PLAN, AS AMENDED

Ladies and Gentlemen:

     We have assisted Advanced Magnetics, Inc. (the "Company"), a Delaware
corporation, in the preparation of a Registration Statement on Form S-8 (the
"Registration Statement") to be filed with the Securities and Exchange
Commission in connection with the registration of 200,000 shares (the "Shares")
of the Company's Common Stock, $.01 par value per share, issuable under the
Company's 1993 Stock Plan (the "Plan"), as that number may be adjusted from time
to time pursuant to the provisions of the Plan.

     We have examined the Certificate of Incorporation of the Company, as
amended, the By-Laws of the Company, as amended, and originals, or copies
certified to our satisfaction, of all pertinent records of the meetings of the
directors and stockholders of the Company, the Registration Statement and such
other documents relating to the Company as we have deemed material for the
purposes of this opinion.

     In examination of the foregoing documents, we have assumed the genuineness
of all signatures and the authenticity of all documents submitted to us as
originals, the conformity to original documents of all documents submitted to us
as certified, photostatic or facsimile copies, and the authenticity of the
originals of any such documents. We have further assumed that all information
contained in all documents reviewed by us is true and complete and that each
grant of an award pursuant to the Plan will be duly authorized.

     Based on the foregoing, we are of the opinion that the Shares have been
duly authorized for issuance under the Plan, and the Shares, when issued and
paid for in accordance with the terms of the Plan and at a price per share in
excess of the par value per share for such Shares, will be legally issued,
fully-paid and nonassessable.

     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. Please
note that we are opining as to the matters expressly set forth herein, and no
opinion should be inferred as to any other matters. This opinion is solely for
your benefit in




Advanced Magnetics, Inc.
November 1, 2001
Page 2


connection with the filing of the Registration Statement and may not be quoted
or relied upon by any other person or used for any other purpose, without our
prior written consent.

     We hereby consent to the filing of this opinion with the Securities and
Exchange Commission in connection with the Registration Statement in accordance
with the requirements of Item 601(b)(5) of Regulation S-K under the Securities
Act of 1933, as amended (the "Securities Act").

                                    Very truly yours,


                                    /S/ WHITE & MCDERMOTT, P.C.
                                    --------------------------------------------
                                    WHITE & MCDERMOTT, P.C.