EXHIBIT 99.1

        BioSource Reports Third Quarter 2004 Financial Results

    CAMARILLO, Calif.--(BUSINESS WIRE)--Oct. 22, 2004--BioSource
International, Inc. (Nasdaq:BIOI) today announced financial results
for its third quarter ended September 30, 2004.
    For the third quarter ended September 30, 2004, the Company
reported net sales of $11.3 million, compared with net sales of $10.7
million for the comparable quarter of 2003. In the third quarter of
2004, foreign exchange rates favorably impacted revenues by $0.3
million. Net income for the third quarter of 2004 was breakeven as
compared to a net loss of $0.1 million, or ($0.01) per share, for the
2003 third quarter.
    For the nine months ended September 30, 2004, net sales were $35.5
million, a 7% increase as compared to net sales of $33.4 million for
the first nine months of fiscal 2003. Without the beneficial impact of
foreign exchange for the nine months ended September 30, 2004, net
sales would have grown 4%. Net income for the first nine months of
fiscal 2004 was $1.2 million, or $0.12 per diluted share, as compared
to net income for the first nine months of fiscal 2003 of $0.3
million, or $0.04 per diluted share.
    Terrance J. Bieker, President and CEO, stated, "We are encouraged
by the 14% increase in sales of our cellular pathway assays during the
third quarter and the significant improvement in our year-over-year
earnings. This supports our heightened business focus on the assays
and related biologicals for the study of disease."

    Third Quarter Review

    Sales of the Company's cellular pathway assay products increased
14% and 13% for the three and nine months ended September 30, 2004,
respectively, compared to the same periods in the prior year. Related
biological product sales decreased 4% during the third quarter of 2004
but increased 5% for the first nine months of 2004 compared to 2003.
In addition, sales of other product lines increased 6% and 3% for the
three and nine months ended September 30, 2004, respectively, as
compared to the same periods in 2003.
    Cost of goods sold increased to $5.6 million in the third quarter
of 2004 from $5.1 million in the third quarter of 2003. The gross
margin of 51% in the third quarter of 2004 decreased from 53% in the
comparable quarter of the prior year due primarily to lower margins in
the Company's custom businesses.
    Operating expenses in the third quarter were as follows:

    --  Research and development expenses were $1.5 million in the
        third quarter of 2004 as compared with $1.7 million in the
        comparable quarter of 2003. This decrease was primarily due to
        headcount reduction and related costs and is consistent with
        the Company's strategy of focusing its R&D investments on its
        core strength of assay development.

    --  In the third quarter of 2004, sales and marketing expenses
        increased to $2.5 million as compared to $2.2 million in the
        third quarter of 2003. This change was due to increased
        expenditures for personnel.

    --  General and administrative expenses of $1.7 million in the
        third quarter of 2004 were relatively consistent with the
        third quarter of 2003 costs.

    At September 30, 2004, the Company's cash and cash equivalents
totaled $4.1 million. The Company announced a stock repurchase program
in July 2004. During the third quarter of 2004, the Company
repurchased approximately $2.5 million of the Company's common stock.
    As previously announced, a live webcast of BioSource
International, Inc.'s third quarter financial results conference call
will be available over the Internet through its Web site at
www.biosource.com in the Investor Relations section beginning today,
October 22, at 10:00 a.m. PDT. A replay of the call will be available
at the same site shortly after the call.
    Event archives are normally available one to two hours after the
event ends. For the live event, listeners should go to the Web site at
least fifteen minutes before the event starts to download and install
any necessary audio software.

    About BioSource International, Inc.

    BioSource International, Inc. is a broad-based life sciences
company focused on providing integrated solutions in the areas of
functional genomics, proteomics, and drug discovery through the
development, manufacturing, marketing, and distribution of unique,
biologically active reagent systems which facilitate, enable, and
accelerate pharmaceutical development and biomedical research. For
more information, please visit the Company's Web site at
www.biosource.com.

    Statements included in this release that are not historical facts
may be considered forward-looking statements that are subject to a
variety of risks and uncertainties. In addition, readers are urged to
consider statements that include the terms "believes," "belief,"
"expects," "plans," "objectives," "anticipates," "intends," "targets,"
"projections," or the like to be uncertain and forward looking. For
these statements, we claim the safe harbor for "forward-looking
statements" within the meaning of the Private Securities Litigation
Reform Act of 1995. Factors that could cause actual results to differ
and vary materially from expectations include, but are not limited to,
our ability to expand our product offerings and any transition to new
products, product quality and availability, any change in business
conditions, changes in our sales strategy and product development
plans, competitive pricing pressures, continued market acceptance of
our products, name recognition of our products, delays in the
development of new technology, possible invalidity or infringement
issues related to intellectual property or proprietary rights, changes
in customer buying patterns, one-time events, and other important
factors disclosed previously and from time to time in our filings with
the Securities and Exchange Commission. These factors should not be
construed as exhaustive or as any admission regarding the adequacy of
disclosures made by us. We cannot always predict or determine after
the fact what factors would cause actual results to differ materially
from those indicated by the forward-looking statements or other
statements. We do not undertake any obligation to publicly update or
revise any forward-looking statements, whether as a result of new
information, future events, or otherwise.


                     BIOSOURCE INTERNATIONAL, INC.
              Condensed Consolidated Statements of Income
             (Amounts in thousands, except per share data)

                                 Three Months Ended  Nine Months Ended
                                    September 30,      September 30,
                                   2004     2003     2004     2003
                                    (Unaudited)       (Unaudited)

Net sales                          $11,308  $10,744  $35,548  $33,377

Cost of goods sold                   5,568    5,079   16,516   15,160

     Gross profit                    5,740    5,665   19,032   18,217

Operating expenses:
  Research and development           1,455    1,687    4,255    5,530
  Sales and marketing                2,493    2,188    7,355    7,064
  General and administrative         1,672    1,729    5,712    4,664
  Amortization of intangibles          139      145      416      435
     Total operating expenses        5,759    5,749   17,738   17,693

Income (loss) from operations          (19)     (84)   1,294      524

Interest and other income
 (expense), net                         25      (21)      13      (75)

Income (loss) before provision for
 income taxes                            6     (105)   1,307      449

Provision (benefit)  for income
 taxes                                 (32)     (24)     115      103

Net income (loss)                  $    38  $   (81) $ 1,192  $   346

Earnings per share:

  Basic                            $  0.00  $ (0.01) $  0.13  $  0.04
  Diluted                          $  0.00  $ (0.01) $  0.12  $  0.04

Shares used in per share
 calculations:

  Basic                              9,322    9,181    9,384    9,418
  Diluted                            9,547    9,181    9,673    9,729


                     BIOSOURCE INTERNATIONAL, INC.
                 Condensed Consolidated Balance Sheets
                              (Unaudited)
                            (in thousands)

                                        September 30,   December 31,
                                            2004           2003
Assets

Current assets
  Cash and cash equivalents             $       4,099  $        3,297
  Accounts receivable, net                      6,600           6,308
  Inventories, net                              8,356           9,074
  Other current assets                          3,331           3,015

     Total current assets                      22,386          21,694

Property and equipment, net                     5,968           6,235

Intangible assets, net                          5,392           5,807

Deferred income taxes                          10,078          10,078

Other assets                                      572             519

     Total assets                       $      44,396  $       44,333

Liabilities and Stockholders' Equity

Current liabilities
  Accounts payable and accrued expenses $       5,941  $        5,678
  Other current liabilities                       839             353

     Total current liabilities                  6,780           6,031

Stockholders' equity                           37,616          38,302

     Total liabilities and
      stockholders' equity              $      44,396  $       44,333

    CONTACT: BioSource International, Inc.
             Alan Edrick, 805-383-5249