7% CONVERTIBLE DEBENTURE DUE AUGUST 30, 2007


$3,000,000                                                    September 26, 1997
                                                              New York, New York

                  FOR VALUE RECEIVED,  ADVANCED VIRAL RESEARCH CORP., a Delaware
corporation (the "undersigned" or the "Company"),  hereby promises to pay to the
order of RBB Bank AG, at its  offices  located  at c/o ABN AMRO Bank  N.V.,  New
York,  New York or at such other place as the holder  hereof shall  designate to
the  undersigned in writing,  in lawful money of the United States of America or
in New York Clearing House Funds, the principal amount of Three Million Dollars,
and to pay  interest  (computed  on the basis of a 360- day year and the  actual
number of days  elapsed) on the unpaid  principal  amount  hereof at the rate of
seven (7%) percent per annum. The undersigned promises to pay the said principal
sum and interest as follows:

                  Until this  Debenture is  completely  retired the  undersigned
shall make  payments of accrued  interest on this  Debenture on the first day of
January and July in each year (commencing with January 1, 1998), computed at the
rate of 7% per annum on the unpaid  principal  balance of this Debenture for the
period from the date of this Debenture until the date of such interest  payment.
On August 30, 2007 the undersigned shall pay the holder all unpaid principal and
interest on this Debenture.

                  Interest on the indebtedness evidenced by this Debenture after
default or maturity  accelerated  or  otherwise  shall be due and payable at the
rate of ten (10%) percent per annum,  subject to the  limitations  of applicable
law.

                  If this  Debenture or any  installment  hereof becomes due and
payable on a Saturday,  Sunday or public  holiday under the laws of the State of
New York, the due date hereof shall be extended to the next succeeding  business
day and  interest  shall be payable at the rate of seven (7%)  percent per annum
during such  extension.  All  payments  received by the holder  shall be applied
first to the payment of all accrued interest payable hereunder.

                  Subject to and in compliance with the provisions  hereof,  the
holder  shall  have the right to  convert  all or a portion  of the  outstanding
principal  amount of this  Debenture into such number of shares of Common Stock,
par value  $.00001 per share,  of the Company  ("Common  Stock")  (the shares of
Common Stock issuable upon conversion of this Debenture are hereinafter referred
to as the "Conversion  Shares") as shall equal the quotient obtained by dividing
(x) the principal amount of this Debenture to be converted by (y) the Applicable
Conversion  Price (as  hereinafter  defined) and by surrender of this Debenture,
such surrender to be made in the manner provided herein; provided, however, that
the right to convert outstanding  principal of this Debenture shall terminate at
the close of business on the third  calendar  day  preceding  the date fixed for
prepayment unless the Company shall default in making such prepayment.






         For purposes hereof the term "Applicable  Conversion  Price" shall mean
the lesser of (q) $0.26 and (r) the  product  obtained  by  multiplying  (i) the
Average Closing Price (as hereinafter defined) by (iii) .70.

         For  purposes  hereof the "Average  Closing  Price" with respect to any
conversion  elected to be made by the holder  shall be the  average of the daily
closing  prices for the five  consecutive  trading days ended on the trading day
immediately  preceding  the date on which the holder gives the Company a written
notice  of the  holder's  election  to  convert  outstanding  principal  of this
Debenture. The closing price on any trading day shall be (a) if the Common Stock
is then listed or quoted on either the NASD Bulletin Board,  the NASDAQ SmallCap
Market or the NASDAQ  National  Market,  the reported  closing bid price for the
Common  Stock on such day or (b) if the  Common  Stock is listed  on either  the
American  Stock  Exchange or New York Stock  Exchange,  the last reported  sales
price for the Common Stock on such exchange on such day.

         On the date notice is  delivered  in order to exercise  its  conversion
right,  the holder shall  surrender this Debenture to the Company at its office,
accompanied  by written  notice to the Company that the holder  hereof elects to
convert  all  or a  specified  portion  of the  outstanding  principal  of  this
Debenture (the "Conversion Notice"). Within five (5) business days after receipt
of this Debenture and the Conversion  Notice, the Company will pay to the holder
all interest  accrued on the principal  amount of this Debenture to be converted
to the effective date of conversion or, at the sole option of the Company, issue
to the holder in lieu thereof such  additional  number of shares of Common Stock
as shall equal the  quotient  obtained by dividing  the total  amount of accrued
interest  on the  principal  amount of this  Debenture  to be  converted  by the
Applicable  Conversion Price.  Within five (5) business days after the surrender
of this  Debenture as aforesaid,  the Company shall cause its transfer  agent to
issue and deliver to such holder,  or on its written  order,  a  certificate  or
certificates  without any restrictive legend thereon for the number of shares of
Common  Stock  issuable  upon  the  conversion  hereof  in  accordance  with the
provisions of this Debenture,  and any fractional interest in respect of a share
of Common Stock  arising upon such  conversion  shall be settled as  hereinafter
provided.  If the  Company  fails to  deliver  to the  holder a  certificate  or
certificates  for shares of Common Stock as aforesaid prior to the expiration of
five (5) business days after receipt of the  Conversion  Notice and surrender to
the Company of the Debenture, the Company shall pay to the holder a penalty. The
penalty shall be $1,000 if the  certificate  or  certificates  are not delivered
until the sixth business day after the delivery of the Conversion Notice and the
penalty shall double every business day until the  certificate  or  certificates
are so  delivered,  but in no event  shall such  penalty  exceed  $100,000.  For
example,  if the  certificates  are  delivered on the eighth  business day after
delivery of the  Conversion  Notice and  surrender of the  Debenture the penalty
shall be $4,000.

         If the entire  outstanding  principal  amount of this  Debenture is not
converted,  the  Company  shall  also  issue and  deliver  to such  holder a new
Debenture of like tenor in the principal amount equal to the principal which was
not converted and dated the effective date of conversion.  Each conversion shall
be deemed to have been  effected  immediately  prior to the close of business on
the date on which this  Debenture  shall have been  surrendered  and such notice
received by the Company as aforesaid, and the person or persons in whose name or
names any  certificate  of  certificates  for  shares of Common  Stock  shall be
issuable  upon such  conversion  shall be deemed to have  become  the  holder or
holders of record of the shares  represented  thereby at such time on such date.
All shares of Common Stock delivered upon


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conversion of this Debenture will, upon delivery,  be duly  authorized,  validly
issued and fully paid and  nonassessable.  No fractional  shares of Common Stock
shall be issued upon  conversion of this  Debenture.  Instead of any  fractional
share of Common Stock which would  otherwise be deliverable  upon the conversion
of a principal of this  Debenture  the Company shall pay to the holder an amount
in cash  (computed  to the  nearest  cent) equal to the  Average  Closing  Price
multiplied  by the  fraction  of a share of  Common  Stock  represented  by such
fractional interest.

         Notwithstanding anything to the contrary contained herein, (w) until 60
days after the Closing  Date (as defined in the  Securities  Purchase  Agreement
dated  September  26, 1997  between  the Company and RBB Bank AG (the  "Purchase
Agreement")) the holder may not elect to convert any portion of the principal of
this  Debenture,  (x) until 90 days  after the  Closing  Date the holder may not
elect  to  convert  more  than  25% of the  original  principal  amount  of this
Debenture, (y) until 120 days after the Closing Date the holder may not elect to
convert more than 50% of the original principal amount of this Debenture and (z)
until 150 days after the Closing  Date the holder may not elect to convert  more
than 75% of the original principal amount of this Debenture.

                  The issuance of  certificates  for shares of Common Stock upon
any  conversion  of this  Debenture  shall be made  without  charge to the payee
hereof  for  any  tax or  other  expense  in  respect  to the  issuance  of such
certificates,  all of which taxes and expenses shall be paid by the Company, and
such  certificates  shall be issued only in the name of the registered holder of
this Debenture.

                  This  Debenture  has  been  issued  pursuant  to and  shall be
subject  to all of the  provisions  of the  Purchase  Agreement.  The  payee  is
entitled to the benefits of the Purchase  Agreement,  and this  Debenture may be
prepaid as provided in the Purchase Agreement. Reference is made to Sections 7.2
and 7.3 of the Purchase  Agreement  with respect to certain rights of the holder
to  convert  this  Debenture  into  Common  Stock  upon  receipt  of a notice of
prepayment.

                  Upon  the  occurrence  of any  one or more  of the  events  of
default  specified  or referred  to in the  Purchase  Agreement  or in the other
documents or  instruments  executed in  connection  therewith,  all amounts then
remaining  unpaid on this  Debenture may be declared to be  immediately  due and
payable as provided in the Purchase Agreement.

                  In the event that this Debenture  shall be placed in the hands
of an attorney for collection by reason of any event of default  hereunder,  the
undersigned agrees to pay reasonable attorney's fees and disbursements and other
reasonable  expenses  incurred by the payee in connection with the collection of
this Debenture.

                  The rights,  powers and remedies given to the payee under this
Debenture shall be in addition to all rights, powers and remedies given to it by
virtue of the  Purchase  Agreement,  any  document  or  instrument  executed  in
connection therewith, or any statute or rule of law.

                  Any  forbearance,  failure or delay by the payee in exercising
any right,  power or remedy under this Debenture,  the Purchase  Agreement,  any
documents or instruments executed in connection therewith or otherwise available
to the payee shall not be deemed to be a waiver


                                        3




of such right,  power or remedy, nor shall any single or partial exercise of any
right, power or remedy preclude the further exercise thereof.

                  No  modification or waiver of any provision of this Debenture,
the Purchase  Agreement or any documents or  instruments  executed in connection
therewith  shall be  effective  unless it shall be in writing  and signed by the
payee,  and any such  modification  or waiver  shall apply only in the  specific
instance for which given.

                  This  Debenture and the rights and  obligations of the parties
hereto,  shall be governed,  construed and interpreted  according to the laws of
the State of New York,  and the  undersigned  consents and agrees that the State
and Federal Courts which sit in the State of New York,  County of New York shall
have exclusive jurisdiction of all controversies and disputes arising hereunder.

                  The term "payee" as used herein shall be deemed to include the
payee and its successors, endorsees and assigns.

                  The undersigned hereby waives presentment, demand for payment,
protest, notice of protest and notice of non-payment hereof.


                               By:
                                   Shalom Z. Hirschman, M.D., President and
                                   Chief Executive Officer