Exhibit 99.1

          Cerus Corporation Announces First Quarter Results

    CONCORD, Calif.--(BUSINESS WIRE)--May 3, 2004--Cerus Corporation
(Nasdaq:CERS) today announced results for the first quarter ended
March 31, 2004.
    The net loss for the first quarter of 2004 was $9.2 million, or
$0.42 per share, compared to a net loss of $17.2 million, or $1.07 per
share, for the first quarter of 2003. The reduction in the net loss
for the quarter was due primarily to increased funding received under
cooperative agreements with the U.S. Armed Forces and reduced
operating expenses. Total revenue from government grants and
development agreements was $3.6 million for the first quarter of 2004,
compared to $1.3 million for the first quarter of 2003.
    At March 31, 2004, the company had cash, cash equivalents and
short-term investments of $99.4 million.
    Loan principal and accrued interest under a credit facility with
Baxter Capital Corporation is classified as a current liability on the
balance sheet, due to a dispute concerning the timing of repayment.
    In a separate press release earlier today, the company announced
the appointment of Claes Glassell as president and chief executive
officer, effective May 10, 2004.
    Cerus and subsidiaries of Baxter International Inc. are
collaborating on development of the INTERCEPT Blood System to enhance
the safety of blood transfusions. The INTERCEPT Blood System for
platelets is being commercialized in Europe. The product is not yet
approved in the United States.
    In April 2004, Cerus and MedImmune, Inc. announced an agreement to
develop a therapeutic vaccine for cancer. Under the terms of the
agreement, MedImmune is responsible for clinical testing,
manufacturing and commercialization of any product resulting from the
collaboration. Cerus will receive an up-front payment of $1.0 million
and will participate in the development of the therapeutic vaccine.
The agreement also provides for Cerus to receive development funding,
as well as milestone payments and royalties on future product sales.

    QUARTERLY CONFERENCE CALL

    The company has scheduled its quarterly conference call for 4:30
p.m. EDT today. Interested parties can access a live Internet
broadcast at http://www.cerus.com/pages/IR/wc.html. For those unable
to listen to the live broadcast, the call will be archived at
www.cerus.com.

    ABOUT CERUS

    Cerus Corporation is developing novel technologies to provide
safer and more effective options to patients in areas with substantial
unmet medical needs. Cerus' most advanced program is the INTERCEPT
Blood System, designed to enhance the safety of the world's blood
supply by inactivating viruses, bacteria, other pathogens and white
blood cells. The INTERCEPT Blood System, which is being developed in
collaboration with subsidiaries of Baxter International Inc., is based
on the company's Helinx technology for controlling biological
replication. The Concord, California-based company also is pursuing
novel therapeutic vaccine technologies, which are being developed to
harness the power of the immune system against cancer and infectious
disease. Cerus has an agreement with MedImmune, Inc. to co-develop and
commercialize a therapeutic vaccine designed to treat cancers of the
breast, prostate and colon, as well as metastatic melanomas.

    Helinx is a trademark of Cerus Corporation.
    INTERCEPT and INTERCEPT Blood are trademarks of Baxter
International Inc.

    Statements in this news release regarding potential efficacy of
products, product development and commercial potential, possible
outcomes of the loan dispute, and the company's relationship with
subsidiaries of Baxter International Inc. are forward-looking
statements that involve risks and uncertainties. Actual results could
differ materially from the above forward-looking statements as a
result of certain factors, including the risks and uncertainty of the
timing and results of clinical trials and other development
activities, actions by regulatory authorities at any stage of the
development process, additional financing activities, manufacturing,
market acceptance of any products, competitive conditions, long term
growth opportunity of Cerus, legal proceedings, actions by Baxter and
other factors discussed in the company's most recent filings with the
Securities and Exchange Commission.


                           CERUS CORPORATION
               SELECTED UNAUDITED FINANCIAL INFORMATION

Condensed Statements of Operations              Three Months Ended
(in thousands, except per share information)         March 31,
                                                2004         2003
                                             ------------ ------------

Revenue                                           $3,647       $1,269

Operating expenses:
  Research and development                         8,668       14,695
  General and administrative                       3,043        2,695
                                             ------------ ------------
    Total operating expenses                      11,711       17,390
                                             ------------ ------------
      Loss from operations                        (8,064)     (16,121)
Interest income (expense), net                    (1,130)      (1,038)
                                             ------------ ------------
      Net loss                                    (9,194)     (17,159)
                                             ============ ============

Net loss per share -- basic and diluted           ($0.42)      ($1.07)
                                             ============ ============
Shares used in computing net loss per share
 -- basic and diluted                             22,084       15,964
                                             ============ ============


Condensed Balance Sheets                      March 31,   December 31,
(in thousands)                                  2004         2003
                                             ------------ ------------

Cash, cash equivalents and short-term
 investments                                     $99,446     $110,010
Accounts receivable from a related party              29            8
Accounts receivable and other current assets       7,313        5,736
Furniture and equipment, net                       1,867        2,553
Other assets                                         131          156
                                             ------------ ------------

  Total assets                                  $108,786     $118,463
                                             ============ ============


Accounts payable to a related party               $2,099       $3,156
Current loan and interest payable to a
 related party                                    57,272       55,834
Other current liabilities                          5,951        6,945
Stockholders' equity                              43,464       52,528
                                             ------------ ------------

  Total liabilities and stockholders' equity    $108,786     $118,463
                                             ============ ============

    CONTACT: Cerus Corporation
             Greg W. Schafer, 925-288-6109