[LETTERHEAD OF SILVERMAN, COLLURA & CHERNIS, P.C.]



                                                                   April 9, 1997


Hemispherx Biopharma, Inc.
1617 JFK Boulevard
Philadelphia, Pennsylvania 19103

        Re: Post-Effective Amendment No. 1 to Registration Statement on Form S-1

Gentlemen:

     We have acted as counsel to Hemispherx Biopharma,  Inc. (the "Company"),  a
Delaware  corporation,  pursuant  to  Post-Effective  Amendment  No.  1  to  the
Registration  Statement on Form S-1, as filed with the  Securities  and Exchange
Commission on April 9, 1997 (the "Registration Statement"), covering (i) 310,544
warrants  and stock  options;  (ii) 179,931  shares of Common  Stock  underlying
warrants;  (iii) 150,000 shares of Common Stock  underlying  warrants;  and (iv)
2,500,000 shares of Common Stock,  underlying Series E Preferred Stock, $.01 par
value.  The Common Stock,  warrants,  stock options and Series E Preferred Stock
are hereinafter collectively referred to as the "Securities".

     In acting as counsel  for the  Company  and  arriving  at the  opinions  as
expressed below, we have examined and relied upon originals or copies, certified
or otherwise  identified  to our  satisfaction,  of such records of the Company,
agreements and other instruments,  certificates of officers and  representatives
of the Company,  certificates of public officials and other documents as we have
deemed necessary or appropriate as a basis for the opinions expressed herein.

     In connection  with our  examination we have assumed the genuineness of all
signatures,  the authenticity of all documents tendered to us as originals,  the
legal capacity of natural  persons and the  conformity to original  documents of
all documents submitted to us as certified or photostated copies.

     Based on the foregoing,  and subject to the  qualifications and limitations
set forth herein, it is our opinion that:

          1. The Company has authority to issue the Securities in the manner and
     under the terms set forth in the Registration Statement.



Hemispherx Biopharma, Inc.
April 9, 1997
Page 2


          2. The Securities have been duly authorized and when issued, delivered
     and paid for in accordance  with their  respective  terms,  will be validly
     issued, fully paid and non-assessable.

     We  express  no  opinion  with  respect to the laws other than those of the
State of New York and  Federal  Laws of the  United  States of  America,  and we
assume on responsibility as to the applicability thereto, the effect thereon, of
the laws of any other jurisdiction.

     We hereby  consent  to the filing of this  opinion  as  Exhibit  5.1 to the
Registration Statement and its use as part of the Registration Statement.

     We are  furnishing  this  opinion to the Company  solely for its benefit in
connection with the Registration  Statement.  It is not to be used,  circulated,
quoted or otherwise referred to for any other purpose. Other than the Company no
one is entitled to reply on this opinion.


                                Very truly yours,

                                /s/ SILVERMAN, COLLURA & CHERNIS, P.C.
                                -----------------------------------------------
                                SILVERMAN, COLLURA & CHERNIS, P.C.