POWER OF ATTORNEY
                         For Executing Forms 3, 4 and 5


     Know all by these  presents,  that the undersigned  hereby  constitutes and
appoints each of Michael  Avallone and Rachel Konforty,  signing singly,  his or
her true and lawful attorney-in-fact to:

     (1)  execute  for and on behalf of the  undersigned,  in the  undersigned's
          capacity as an officer  and/or  director of Advanced  Magnetics,  Inc.
          (the "Company"),  Forms 3, 4 and 5 (including any amendments  thereto)
          in  accordance  with Section 16(a) of the  Securities  Exchange Act of
          1934, as amended and the rules thereunder;

     (2)  do and perform  any and all acts for and on behalf of the  undersigned
          which may be necessary  or desirable to complete the  execution of any
          such  Forms 3, 4 and 5 and the  timely  filing of such  forms with the
          United  States  Securities  and  Exchange  Commission  and  any  other
          authority; and

     (3)  take any other action of any type  whatsoever in  connection  with the
          foregoing  which, in the opinion of such  attorney-in-fact,  may be of
          benefit  to, in the best  interest  of, or  legally  required  by, the
          undersigned,  it being understood that the documents  executed by such
          attorney-in-fact  on behalf of the undersigned  pursuant to this Power
          of  Attorney  shall be in such form and shall  contain  such terms and
          conditions  as  such  attorney-in-fact  may  approve  in  his  or  her
          discretion.

     The undersigned hereby grants to each such  attorney-in-fact full power and
authority  to do and perform all and every act and thing  whatsoever  requisite,
necessary  and proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally  present,  with full power of substitution or revocation,
hereby  ratifying and confirming all that such  attorney-in-fact,  or his or her
substitute or  substitutes,  shall  lawfully do or cause to be done by virtue of
this Power of Attorney and the rights and powers herein granted. The undersigned
acknowledges that the foregoing  attorneys-in-fact,  in serving in such capacity
at  the  request  of the  undersigned,  are  not  assuming,  nor is the  Company
assuming, any of the undersigned's responsibilities to comply with Section 16 of
the Securities Exchange Act of 1934, as amended.

     This Power of  Attorney  shall  remain in full  force and effect  until the
undersigned  is no longer  required to file Forms 3, 4 and 5 with respect to the
undersigned's  holdings of and transactions in securities issued by the Company,
unless earlier revoked by the  undersigned in a signed writing  delivered to the
foregoing attorney-in-fact.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 21 day of July, 2004.





                                         Signed: /s/ Brian J. G. Pereira

                                         Please print: Brian J. G. Pereira