[CYTOGEN LOGO]


COMPANY CONTACT:
Cytogen Corporation
Stacy Shearer
Investor Relations
(609) 750-8289
sshearer@cytogen.com


    CYTOGEN REPORTS RECORD PRODUCT REVENUES IN THE FIRST QUARTER OF 2004 AND
                  REAFFIRMS 2004 FULL YEAR FINANCIAL GUIDANCE

 Year-over-year growth from both QUADRAMET(TM) and PROSTASCINT(R) drives record
                        product revenues for the quarter

PRINCETON,  N.J.,  (MAY 4,  2004)  --  Cytogen  Corporation  (Nasdaq:  CYTO),  a
product-driven,  oncology-focused  biopharmaceutical company, today reported its
consolidated financial results for the first quarter ended March 31, 2004.

Total revenues for the first quarter of 2004 were $3.6 million  compared to $2.5
million in the first  quarter of 2003,  with product  revenues  increasing  to a
record $3.6  million  from $1.9  million in the first  quarter of 2003.  Cytogen
reported a net loss of $4.3 million or $0.33 per basic and diluted share for the
first  quarter of 2004 compared to a net loss of $2.0 million or $0.22 per basic
and diluted share for the same period in 2003.

"We continue to aggressively  pursue expanded use and new clinical  applications
for both QUADRAMET(TM) and PROSTASCINT(R), and are proud of the growth exhibited
from these  products  over the prior  year's  first  quarter,"  said  Michael D.
Becker,  Cytogen's  President and Chief Executive  Officer.  "We are also adding
resources to enhance our sales and  marketing  infrastructure  as evidenced by a
greater than 50%  increase in oncology  field  representatives  since the August
2003  reacquisition of North and Latin America marketing rights to QUADRAMET and
the recent addition of Tom Lytle as Senior Vice President of Sales and Marketing
to oversee  strategic  sales and  marketing  initiatives  for both  existing and
future oncology products,  such as COMBIDEX(R).  Finally, to further support all
of these  activities,  we recently raised  approximately  $24 million in capital
from recognized institutional investors."

Product Revenue

QUADRAMET

Sales of QUADRAMET  (samarium Sm-153  lexidronam  injection),  a unique skeletal
targeting  therapeutic  radiopharmaceutical  for the  relief of pain due to bone
metastases  arising from prostate,  breast,  multiple myeloma and other types of
cancer, were $1.9 million for the first quarter of 2004.

Under a 1998 agreement,  Berlex  Laboratories had marketing rights for QUADRAMET
in North and Latin America. Through July 31, 2003, Cytogen received and reported
royalties on product  sales made by Berlex.  Such royalty  revenue from sales of
QUADRAMET during the first quarter of 2003 was $449,000.

On August 1, 2003,  Cytogen  reacquired  these  marketing  rights from Berlex in
exchange  for an upfront cash  payment of $8.0  million and  royalties  based on
future sales of QUADRAMET. At that time, Cytogen began recording product revenue
from the sales of QUADRAMET.


                            QUADRAMET REVENUE SUMMARY
                                 ($ in millions)

                  2003       2003        2003        2003        2004
                   Q1         Q2          Q3          Q4          Q1
Product Sales      n/a        n/a        $1.2        $1.6        $1.9
Royalties         $0.4       $0.5        $0.2         n/a         n/a
                  ----       ----        ----        ----        ----
TOTAL:            $0.4       $0.5        $1.4        $1.6        $1.9

PROSTASCINT

Sales of  PROSTASCINT  (capromab  pendetide),  the  first  and  only  commercial
monoclonal  antibody-based  molecular imaging agent targeting  prostate-specific
membrane  antigen,  or PSMA,  were $1.7  million  in the first  quarter  of 2004
compared to $1.6 million in the first quarter of 2003.

During 2003,  Cytogen collected and presented data to the Centers for Medicare &
Medicaid Services (CMS)  demonstrating the need for change in the relative value
of PROSTASCINT for the hospital outpatient prospective payment system (HOPPS). A
more appropriate higher PROSTASCINT reimbursement value was established for 2004
that the Company  believes will help ensure that  hospitals are not  discouraged
from providing  Medicare  beneficiaries  access to this important and clinically
useful molecular imaging procedure.

                           PROSTASCINT REVENUE SUMMARY
                                  ($ in millions)

                  2003        2003        2003        2003        2004
                   Q1          Q2          Q3          Q4          Q1
Product Sales     $1.6        $1.6        $1.5        $1.8        $1.7

Other product revenues

Other  product  revenues,  consisting  of  brachytherapy  products  and NMP22(R)
BLADDERCHEK(R) (nuclear matrix protein-22), a point-of-care, in vitro diagnostic
test for bladder cancer  developed by Matritech,  Inc.,  were not significant in
the first  quarter of 2004 compared to $265,000 in the first quarter of 2003. As
previously  announced,  Cytogen discontinued  marketing  brachytherapy  products
effective  January 24,  2003.  From  November  2002  through  December 31, 2003,
Cytogen promoted NMP22 BLADDERCHEK primarily to urologists in the United States.
After December 31, 2003, Cytogen has been selling NMP22 BLADDERCHEK  exclusively
to oncologists.

Costs and Expenses

Total operating expenses in the first quarter of 2004 were $7.9 million compared
to $5.0  million  in the  first  quarter  of 2003.  Operating  expenses  in 2004
reflect,  among other items,  QUADRAMET  and  PROSTASCINT  manufacturing  costs,
royalties paid by Cytogen to Dow Chemical and Berlex  Laboratories  on our sales
of  QUADRAMET,  and the  amortization  of the  up-front  payment  to  Berlex  to
reacquire QUADRAMET.  The 2004 operating expenses also include increased selling
and marketing expenses related to the expansion of the Company's sales force and
marketing initiatives for the Company's existing oncology products. The 2004 and
2003 operating  expenses also reflect costs associated with the PSMA Development
Company  LLC  ("PDC"),   a  joint   venture   between   Cytogen  and   Progenics
Pharmaceuticals,  Inc., for the development of in vivo immunotherapies targeting


prostate specific membrane antigen (PSMA).  Cytogen's share of the equity in the
loss  associated with PDC was $809,000 for the first quarter of 2004 compared to
$880,000 in the first quarter of 2003.

Cash Position

Cytogen's cash, cash equivalents and short-term  investments balance as of March
31, 2004 was $25.0 million compared to $30.2 million as of December 31, 2003. In
April 2004, the Company received net proceeds of approximately  $24.0 million in
connection with a registered  direct offering of 2,570,000  shares of its common
stock.

Clinical Development Update

QUADRAMET is currently being evaluated  alone, at higher doses,  and in a series
of  combination  therapy  regimens in order to assess  potential  synergies with
anti-tumor  drugs,  such as docetaxel,  and other bone seeking  agents,  such as
zoledronic acid, based on demonstrated  clinical activity in  hormone-refractory
prostate cancer,  multiple myeloma,  osteosarcoma and other cancers. In addition
to pain palliation,  analyses of data from these investigational monotherapy and
combination  therapy studies  demonstrate that QUADRAMET may have a broader role
as  an  oncolytic   agent  in  a  variety  of  solid  tumor  and   hematological
malignancies,  including acute lymphoblastic  leukemia,  acute myeloid leukemia,
and  myelodysplastic  syndrome.  New  clinical  studies  are  expected  to begin
throughout 2004 with a goal to identify the most promising QUADRAMET programs to
advance.  Data  from  several  investigational  studies  has been  accepted  for
dissemination  at the  upcoming  American  Society of Clinical  Oncology  (ASCO)
Annual Meeting and additional publications and presentations are expected during
2004.

Year-to-date 2004 Highlights

- -    Thomas S.  Lytle  joined  Cytogen  as Senior  Vice  President  of Sales and
     Marketing. Mr. Lytle will oversee strategic sales and marketing initiatives
     for Cytogen's existing and future oncology products.
- -    The  Company  received  net  proceeds  of  approximately  $24.0  million in
     connection  with a registered  direct  offering of 2,570,000  shares of its
     common stock.
- -    Clinical  data  demonstrating  that  overexpression  of   Prostate-Specific
     Membrane Antigen (PSMA) in primary prostate cancer not only correlates with
     other adverse traditional  prognostic factors,  but independently  predicts
     disease  recurrence was published in the journal  Clinical  Cancer Research
     (Volume 9, No. 17, pp. 6357-6362). Overexpression of PSMA in this study was
     determined  by  immunohistochemical  staining  using  the  same  monoclonal
     antibody utilized in PROSTASCINT.
- -    Data derived from Cytogen's proprietary protein interaction  technology was
     published  in the journal  Proteomics  (Volume 4, No. 3, pp.  643-655)  and
     positive  results  from a research  collaboration  between  Cytogen and the
     Kimmel Cancer Institute at Thomas Jefferson University designed to identify
     novel interactions  associated with Wwox, a tumor suppressor  protein,  was
     published in the  Proceedings  of the  National  Academy of Sciences of the
     United States (Volume 101, No. 13, pp. 4401-4406).

Financial Outlook for 2004

The Company reaffirms its previous issued financial guidance as follows:


- -- Reflecting  only QUADRAMET and  PROSTASCINT,  Cytogen  expects an increase in
2004 full year product revenue of approximately 65% to 75% over its 2003 product
revenue of $9.8 million;

- -- In 2004,  Cytogen expects an average gross margin of approximately 40%, which
reflects  QUADRAMET  and  PROSTASCINT  manufacturing  costs and royalties to Dow
Chemical and Berlex Laboratories;

- -- In 2004, Cytogen expects an increase in its full year total selling,  general
and  administrative  expenses of  approximately  55 to 60% compared to the $11.6
million  incurred in these areas in 2003 due primarily to sales force  expansion
and other marketing  initiatives  associated with the  commercialization  of the
Company's existing and anticipated oncology products;

- -- Cytogen  expects  an  increase  in 2004 full year  research  and  development
expenses of  approximately  55% to 60% over its 2003  research  and  development
expenses of $2.7 million due primarily to  investigational  studies  relating to
QUADRAMET; and

- -- In  2004,  Cytogen  expects  an  increase  in its  share of the  equity  loss
associated with the PDC joint venture of  approximately  30% over its 2003 share
of the equity loss of $3.5 million due  primarily  to third party  manufacturing
and  development  costs  related  to  PDC's  monoclonal   antibody  programs  in
preparation for initiation of human clinical trials.

The statements  made in the foregoing  paragraphs  under the heading  "Financial
Outlook  for 2004" are  forward-looking  statements,  subject to the  disclosure
notice paragraph regarding forward-looking statements set forth below.

NOTE:

QUADRAMET  is  indicated  for the  relief  of pain in  patients  with  confirmed
osteoblastic  metastatic  bone lesions that enhance on  radionuclide  bone scan.
This  press  release  describes  clinical  applications  that  differ  from that
reported in the QUADRAMET package insert.

PROSTASCINT  is  indicated  as a  diagnostic  imaging  agent in newly  diagnosed
patients with biopsy-proven  prostate cancer, thought to be clinically localized
after standard diagnostic  evaluation and who are thought to be at high risk for
pelvic  lymph node  metastases.  PROSTASCINT  is also  indicated as a diagnostic
imaging agent in post-prostatectomy patients with a rising PSA and a negative or
equivocal  standard  metastatic  evaluation  in whom  there  is a high  clinical
suspicion of occult metastatic  disease.  This press release describes  clinical
applications  and imaging  performance  that differs  from that  reported in the
PROSTASCINT package insert.

A copy of the full prescribing information for QUADRAMET, PROSTASCINT, and NMP22
BLADDERCHEK may be obtained in the U.S. from Cytogen Corporation by calling toll
free 800-833-3533 or by visiting the web site at  http://www.cytogen.com,  which
is not part of this press release.

About Cytogen Corporation

Founded in 1980,  Cytogen  Corporation  of  Princeton,  NJ is a  product-driven,
oncology-focused  biopharmaceutical  company that develops and  commercializes a
balanced  portfolio of oncology products that address the unmet medical needs of
patients  and  the  physicians  that  serve  them.   Cytogen   directly  markets
QUADRAMET(TM) (samarium Sm-153 lexidronam injection),  PROSTASCINT(R)  (capromab


pendetide) kit for the  preparation  of Indium In-111  capromab  pendetide,  and
NMP22(R)  BLADDERCHEK(R)  (nuclear  matrix  protein-22)  in the  United  States.
Cytogen  has  exclusive   United   States   marketing   rights  to   COMBIDEX(R)
(ferumoxtran-10),  an  investigational  molecular  imaging  agent  consisting of
lymphotropic  superparamagnetic  nanoparticles used in conjunction with magnetic
resonance  imaging to aid in the diagnosis of metastatic  lymph nodes,  which is
under  review  by the  U.S.  Food  and  Drug  Administration.  Cytogen  is  also
developing therapeutics targeting  prostate-specific  membrane antigen (PSMA), a
protein  highly  expressed  on the  surface  of  prostate  cancer  cells and the
neovasculature of solid tumors.  Full prescribing  information for the Company's
products is available at www.cytogen.com or by calling 1-800-833-3533.  For more
information, please visit the Company's website at www.cytogen.com, which is not
part of this press release.


This press release  contains  certain  "forward-looking"  statements  within the
meaning of the Private Securities  Litigation Reform Act of 1995 and Section 21E
of the Securities Exchange Act of 1934, as amended.  All statements,  other than
statements of  historical  facts,  included in this press release  regarding our
strategy,  future operations,  financial  position,  future revenues,  projected
costs,  prospects,  plans  and  objectives  of  management  are  forward-looking
statements.  Such  forward-looking  statements  involve  a number  of risks  and
uncertainties  and investors are cautioned not to put any undue  reliance on any
forward-looking  statement.  There are a number of important  factors that could
cause  Cytogen's  results  to differ  materially  from those  indicated  by such
forward-looking  statements.  In particular,  Cytogen's business is subject to a
number of significant risks, which include,  but are not limited to: the risk of
obtaining  the  necessary  regulatory  approvals;  the risk of whether  products
result  from  development  activities;  the  risk of  shifts  in the  regulatory
environment  affecting  sales of Cytogen's  products such as  third-party  payor
reimbursement  issues;  the risk  associated  with  Cytogen's  dependence on its
partners for development of certain projects, as well as other factors expressed
from time to time in Cytogen's periodic filings with the Securities and Exchange
Commission  (the  "SEC").  As a result,  this  press  release  should be read in
conjunction with Cytogen's  periodic  filings with the SEC. The  forward-looking
statements  contained herein are made only as of the date of this press release,
and Cytogen  undertakes no obligation  to publicly  update such  forward-looking
statements to reflect subsequent events or circumstances.

                                      ###






                       CYTOGEN CORPORATION & SUBSIDIARIES
                (All amounts in thousands except per share data)
                                   (Unaudited)

                 CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS


                                                             THREE MONTHS ENDED
                                                                  MARCH 31,
                                                         --------------------------
                                                            2004             2003
                                                         ---------        ---------
                                                                    
Revenues:
   Quadramet                                              $  1,854        $      -
   ProstaScint                                               1,727           1,620
   Other                                                         1             265
                                                          --------        --------
          Total Product Revenue                              3,582           1,885
                                                          --------        --------

   Royalty Revenue                                               -             449
   License and Contract Revenue                                 19             143
                                                          --------        --------
          Total Revenues                                     3,601           2,477
                                                          --------        --------

Operating Expenses:
   Cost of Product Related Revenue                           2,399             910
   Selling, General and Administrative                       3,755           2,378
   Research and Development                                    940             833
   Equity in Loss of Joint Venture                             809             880
                                                          --------        --------
          Total Operating Expenses                           7,903           5,001
                                                          --------        --------

Interest Income (Expense), Net                                  20             (11)
Income Tax Benefit                                               -            (584)
                                                          --------        --------
Net Loss                                                  $ (4,282)       $ (1,951)
                                                          ========        ========

Basic and Diluted Net Loss Per Share                      $  (0.33)       $  (0.22)
                                                          ========        ========

Weighted Average Common Shares Outstanding                  12,860           8,763
                                                          ========        ========



                      CONDENSED CONSOLIDATED BALANCE SHEETS



                                                         MARCH 31,     DECEMBER 31,
                                                           2004            2003
                                                        ----------     ------------
                                                                    
Assets:
   Cash, Cash Equivalents and Short-Term Investments      $24,986         $30,215
   Accounts Receivable, Net                                 1,257           1,445
   Inventories                                              1,575           1,887
   Property and Equipment, Net                                648             595
   Quadramet License Fee, Net                               7,546           7,720
   Other Assets                                             2,227           1,833
                                                          -------         -------
          Total Assets                                    $38,239         $43,695
                                                          =======         =======

Liabilities and Stockholders' Equity:
   Accounts Payable and Accrued Liabilities               $ 3,901         $ 5,125
   Other Current Liabilities                                   75              76
   Long-Term Liabilities                                    2,485           2,454
   Stockholders' Equity                                    31,778          36,040
                                                          -------         -------
          Total Liabilities and Stockholders' Equity      $38,239         $43,695
                                                          =======         =======