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                                                                    EXHIBIT 10.5

                                 PROMISSORY NOTE

$18,933.94                                                       JULY 31, 2000

         FOR VALUE RECEIVED, the undersigned Maria S. Gawryl, an individual
residing at 256 Marginal Street, East Boston, MA 02128 (the "Obligor"), hereby
absolutely and unconditionally promises to pay to the order of BIOPURE
Corporation, a Delaware corporation ("BIOPURE"), at the office of BIOPURE
located at 11 Hurley Street, Cambridge, MA 02141, on or before October 31, 2002,
the principal sum of Eighteen thousand nine hundred thirty-three dollars and 94
cents ($18,933.94), with interest thereon, or on such part thereof as shall from
time to time remain unpaid, at the Prescribed Rate, compounded annually as of
December 31 of each year.

         The Obligor has the absolute right to prepay in whole or in part the
principal of this Note and any accrued interest without penalty.

         The "Prescribed Rate" shall be, for each full or partial calendar year
during which interest shall accrue hereunder, the rate per annum equal to the
rate of interest announced by Fleet Bank of Massachusetts, N.A. as its base rate
(the "Base Rate") as in effect on January 1 of such calendar year.
Notwithstanding the previous sentence, if Fleet Bank of Massachusetts N.A. shall
announce, at any time during any such calendar year, a Base Rate that is more
than 2% higher of lower than the Base Rate in effect on January 1 of such year,
the Prescribed Rate shall be, for the remainder of such calendar year, the Base
Rate as announced from time to time during the remainder of such calendar year.

         The Obligor hereby concurrently pledges, assigns, transfers and
delivers to BIOPURE as collateral for payment and performance of all obligations
under this Note, the Obligor's interest in Biopure Associates Limited
Partnership II, a Massachusetts limited partnership representing indirect
ownership of 36,666.6667 shares of the common stock, $.01 par value, of BIOPURE,
together with any applicable assignments appropriately executed in blank. Such
shares of BIOPURE common stock and all other property of the Obligor which is
now or may hereafter be in the possession of control of BIOPURE for any purpose,
together with all additions, replacements, substitutions or proceeds thereof
(all of the foregoing being hereinafter called the "Collateral"), shall
constitute continuing security for any and all of the obligations under this
Note. The holder of this Note may at its option, whether or not this Note is
due, demand, sue for, collect or make any compromise or settlement it deems
desirable with reference to any Collateral.

         Upon the occurrence of any default by the Obligor in the payment or
performance of any of his obligations under this Note, or upon the death or
termination, whether voluntary or involuntary, with cause or without cause, for
any reason, including but not limited to disability or retirement, of the
Obligor's employment, directorial or advisory relationship with BIOPURE,
thereupon or at any time thereafter, at the option of the holder, all
obligations of the Obligor shall become immediately due and payable without

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notice or demand and the holder of this Note shall then have in any jurisdiction
where enforcement hereof is sought, in addition to all other rights and
remedies, the rights and remedies of a secured party under the Uniform
Commercial Code of Massachusetts.

         The Obligor will pay on demand all costs of collection and attorneys
fees paid or incurred by the holder hereof in enforcing the obligations of the
Obligor.

         The Obligor and all endorsers, guarantors and pledgors hereby waive
presentment, demand, notice of dishonor, protest and all other demands and
notices, in connection with the delivery, acceptance, performance, default or
enforcement of this Note, assent to any extension, or postponement of the time
of payment or any other indulgence, to any substitution, exchange or release of
collateral and to the addition of release of any other party or person primarily
or secondarily liable.

         THIS NOTE SHALL BE DEEMED TO TAKE EFFECT AS A SEALED INSTRUMENT IN
ACCORDANCE WITH THE LAWS OF THE COMMONWEALTH OF MASSACHUSETTS AND FOR ALL
PURPOSES SHALL BE GOVERNED BY AND INTERPRETED AND DETERMINED IN ACCORDANCE WITH
SUCH LAWS.

         This Note replaces a promissory note of like tenor dated July 31, 1995,
in the amount of $12,601.93.

         IN WITNESS WHEREOF, the undersigned has executed this Note as of the
day and year first above written.

                                             ___________________________________
                                             Maria S. Gawryl