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                                               EXHIBIT 10.4

                       CYTOGEN CORPORATION

                  CONVERTIBLE PROMISSORY NOTE

U.S. $2,000,000		                      					August 12, 1998
                                            New York, New York

The undersigned, Cytogen Corporation, a Delaware 
corporation with offices at 600 College Road East, Princeton, 
New Jersey 08540 ("Cytogen"), unconditionally promises to pay 
to Elan International Services, Ltd., a Bermuda corporation 
("EIS") or any of its successors or assigns or any other 
holder of this Note (collectively, the "Holder"), on August 
12, 2005 (the "Maturity Date"), at such place as may be 
designated by the Holder to Cytogen, the principal amount of 
$2,000,000, together with interest thereon accrued from and 
after the date hereof, at a rate per annum equal to the lesser 
of (x) 7%, and (y) the maximum rate of interest permitted by 
applicable law, compounded on a semi-annual basis, such 
compounding to commence as of the first cash interest payment 
date as provided in Section 2(b) below.


     SECTION 1.	REORGANISATION AGREEMENT
                ------------------------

(a) This Note is issued pursuant to an unwind 
agreement dated as of the date hereof by and between Cytogen 
and EIS (the "Reorganisation Agreement").  This Note is the 
Convertible Promissory Note referred to in the Reorganisation 
Agreement and the Holder is intended to be afforded the 
benefits thereof, including the Representations and Warranties 
set forth by Cytogen therein.

     SECTION 2.	PAYMENTS
                --------

          (a) Unless earlier converted in accordance with the 
terms of Section 3 below or prepaid in accordance with the 
terms hereof, the entire outstanding principal amount of this 
Note, together with any accrued and unpaid interest thereon, 
shall be due and payable on the Maturity Date.

          (b) During the initial 24-month period from and 
after the date hereof, Cytogen shall not be required to pay 
accrued interest hereon in cash; such accrued interest shall 
be capitalized and added to the principal amount outstanding 
hereunder.  Thereafter, Cytogen shall pay all accrued interest 
to the Holder in cash.

          (c) Principal outstanding hereunder, together with 
accrued and unpaid interest thereon, may be prepaid by Cytogen 
at any time, in whole or in part, upon five-days written 
Notice to the Holder; such payments shall be due and payable 
on the last business day of each of the second and fourth 
calendar quarters of each year, commencing with the calendar 
quarter ending in December 2000.

     SECTION 3. CONVERSION
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          (a) From and after the date hereof and until this 
Note is repaid in full, the Holder shall have the right, in 
its sole discretion, to convert all principal and accrued 
interest then-outstanding hereunder for shares of the common 
stock of Cytogen, par value $.01 per share (the "Common 
Stock"), at a conversion price of $2.80 per share (the 
"Conversion Price"), subject to adjustment as described 
herein.

          (c) The Holder shall be entitled to exercise the 
rights of conversion as described in this Section 3 upon 30 
days Notice to Cytogen, such Notice to be in the form attached 
hereto as Exhibit A.


     SECTION 4.	CERTAIN COVENANTS
                -----------------
                Cytogen covenants and agrees with the Holder 
that, so long as any amount remains unpaid on the Note, unless 
the consent of the Holder is obtained, Cytogen:

          (a)	shall not, prior to the payment in full of the 
outstanding principal, and accrued and unpaid interest on, the 
Note, create, incur, or suffer to exist any indebtedness or 
other obligation senior hereto, other than in the ordinary 
course of business; 

          (b)	shall not change its primary line of business;

          (c)	shall not (i) enter into any merger or 
consolidation, (ii) liquidate, wind up its affairs or 
dissolve, or (iii) except in the ordinary course of business, 
convey, sell, lease, transfer or otherwise dispose of, or 
purchase or acquire, any business, assets, or other property;

          (d)	shall not, directly or indirectly, enter into any 
transaction with, or for the benefit of,  an affiliate (other 
than for reasonable compensation);

          (e)	shall deliver to Holder:

               (i)	promptly after Cytogen shall obtain knowledge 
of the occurrence of any Event of Default (as hereinafter 
defined) or any event which with notice or lapse of time or 
both would become an Event of Default (an Event of Default or 
such other event being a "Default"), a notice specifying that 
such notice is a "Notice of Default" and describing such 
Default in reasonable detail, and, in such Notice of Default 
or as soon thereafter as practicable, a description of the 
action Cytogen has taken or proposes to take with respect 
thereto; and

               (ii)	promptly after Cytogen shall obtain knowledge 
of such, provide written notice of all legal or arbitral 
proceedings, and of all proceedings by or before any 
governmental or regulatory authority or agency, and each 
material development in respect of such legal or other 
proceedings, affecting Cytogen and its subsidiaries; except, 
proceedings which, if adversely determined, would not have a 
material adverse effect on Cytogen and its subsidiaries taken 
as a whole.

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     SECTION 5.	ADJUSTMENT TO CONVERSION PRICE	
                 ------------------------------

     The Conversion Price shall be subject to adjustment from 
time to time as follows:

          (a)	 (i)	If Cytogen shall issue, after the date 
hereof, any Additional Stock (as defined below) without 
consideration or for a consideration per share less than the 
greater of (X) the Conversion Price for such series in effect 
immediately prior to the issuance of such Additional Stock and 
(Y) the Closing Price on such date, the Conversion Price for 
such series in effect immediately prior to each such issuance 
shall forthwith (except as otherwise provided in this clause 
(i)) be adjusted to a price equal to a price determined by 
multiplying such Conversion Price by a fraction, the numerator 
of which shall be the sum of (w) the number of shares of 
Common Stock outstanding immediately prior to such issuance 
and (x) the number of shares of Common Stock that the 
aggregate consideration received by the Corporation for such 
issuance would purchase at such Conversion Price; and the 
denominator of which shall be the sum of (y) the number of 
shares of Common Stock outstanding immediately prior to such 
issuance and (z) the number of shares of such Additional 
Stock.  In the event that the the Conversion Price is 
adjusted, as set forth above, the number of shares of Common 
Stock issuable upon exercise of the conversion right herein 
shall be increased by the reciprocal of such Conversion Price 
adjustment.

               (ii)	No adjustment of the Conversion Price 
shall be made in an amount less than one cent per share, 
provided that any adjustments which are not required to be 
made by reason of this sentence shall be carried forward and 
shall be either taken into account in any subsequent 
adjustment made prior to three years from the date of the 
event giving rise to the adjustment being carried forward, or 
shall be made at the end of three years from the date of the 
event giving rise to the adjustment being carried forward. No 
adjustment of such Conversion Price pursuant to this 
subsection 5(a)(ii) shall have the effect of increasing the 
Conversion Price above the Conversion Price in effect 
immediately prior to such adjustment.

               (iii)	In the case of the issuance of Common 
Stock for cash, the consideration shall be deemed to be the 
amount of cash paid therefor before deducting any reasonable 
discounts, commissions or other expenses allowed, paid or 
incurred by Cytogen for any underwriting or otherwise in 
connection with the issuance and sale thereof.

               (iv)	In the case of the issuance of the Common 
Stock for a consideration in whole or in part other than cash, 
the consideration other than cash shall be deemed to be the 
fair value thereof as determined by Cytogen's board of 
directors irrespective of any accounting treatment.

               (v)	In the event that Cytogen causes its 
Common Stock to be combined, split or effects other capital 
reorganisation that has the effect of changing the number of 
outstanding shares of Common Stock, the number of shares of 
Common Stock issuable upon exercise of the conversion right 
herein shall be adjusted accordingly.

          (b)	"Additional Stock" shall mean any shares of 
Common Stock issued by Cytogen after the Purchase Date to its 

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Affiliates or directors, officers, employees or agents of such 
Affiliates, other than shares of Common Stock issuable or 
issued to employees, consultants or directors of Cytogen 
directly or pursuant to a stock option plan, stock purchase 
plan,  restricted stock plan or contractual obligation 
approved by the Board of Directors of Cytogen (provided that 
the sum of such number of shares of Common Stock issuable or 
issued pursuant to such stock option plan or restricted stock 
plan shall in no event represent more than 20% of the 
authorized number of shares of Common Stock).  "Affiliates" 
shall mean, with respect to any party, any entity that, 
directly or indirectly through one or more intermediaries, 
controls or is controlled by or is under common control with 
such party.  For purposes of this definition, "control" means 
the power to direct or cause the direction of the management 
and policies of an entity, whether through the ownership of 
voting securities, by contract or otherwise.

          (c)	In the event Cytogen should at any time or from 
time to time after the date hereof fix a record date for the 
effectuation of a split or subdivision of the outstanding 
shares of Common Stock or the determination of holders of 
Common Stock entitled to receive a dividend or other 
distribution payable in additional shares of Common Stock or 
other securities or rights convertible into, or entitling the 
holder thereof to receive directly or indirectly, additional 
shares of Common Stock (hereinafter referred to as "Common 
Stock Equivalents") without payment of any consideration by 
such holder for the additional shares of Common Stock or the 
Common Stock Equivalents (including the additional shares of 
Common Stock issuable upon conversion or exercise thereof), 
then, as of such record date (or the date of such dividend 
distribution, split or subdivision if no record date is 
fixed), the Conversion Price shall be appropriately decreased 
so that the number of shares of Common Stock issuable on 
conversion of each share of such series shall be increased in 
proportion to such increase of the aggregate of shares of 
Common Stock outstanding and those issuable with respect to 
such Common Stock Equivalents.

          (d)	If the number of shares of Common Stock 
outstanding at any time after the  date hereof is decreased by 
a combination of the outstanding shares of Common Stock, then, 
following the record date of such combination, the Conversion 
Price shall be appropriately increased so that the number of 
shares of Common Stock issuable on conversion of each share of 
such series shall be decreased in proportion to such decrease 
in outstanding shares.

     SECTION 6.	EVENTS OF DEFAULT
                -----------------

          The occurrence of any of the following events shall 
constitute an event of default (an "Event of Default"):

          (a)	A default in the payment of the principal 
amount of this Note, when and as the same shall become due and 
payable;

          (b)	a default in the payment of any accrued and 
unpaid interest on any Note, when and as the same shall become 
due and payable;

          (c)	a default in the performance, or a breach of 
any other covenant or agreement of Cytogen in this Note, and 

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continuance of such default or breach for a period of 10 days 
after the Holder has notified Cytogen of its occurrence;

          (d)	any representation, warranty, or certification 
made by Cytogen pursuant to this Note or the Reorganisation 
Agreement shall prove to have been false or misleading as of 
the date made in any material respect;

          (e)	 (i) the entry of a decree or order by a court 
having jurisdiction adjudging Cytogen bankrupt or insolvent, 
or approving a petition seeking reorganization, arrangement, 
adjustment or composition of or in respect of Cytogen, under 
United States bankruptcy or insolvency law, as now or 
hereafter constituted, and the continuance of any such decree 
or order unstayed and in effect for a period of 60 days; (ii) 
the commencement by Cytogen of a voluntary case under United 
States bankruptcy law, as now or hereafter constituted, or the 
consent by Cytogen to the institution of bankruptcy or 
insolvency proceedings against it; (iii) the filing by Cytogen 
of a petition or answer or consent seeking reorganization or 
relief under United States bankruptcy law; (v) the appointment 
of a receiver, liquidator, assignee, trustee, or similar 
official of Cytogen or of any substantial part of its property 
which is not discharged within 60 days; (vi) the making by 
Cytogen of an assignment for the benefit of creditors, or the 
admission by it in writing of its inability to pay its debts 
generally as they become due, or the taking of corporate 
action by Cytogen in furtherance of any such action; or 

          (f) a material default by Cytogen under the 
Reorganisation Agreement.

     SECTION 7. REMEDIES IN THE EVENT OF DEFAULT
                --------------------------------

          (a) In the case of any Event of Default by Cytogen, 
the amount of outstanding principal under this Note and 
accrued and unpaid interest thereon shall, in addition to all 
other rights and remedies of the Holder hereunder and under 
applicable law, be and become immediately due and payable upon 
written notice delivered by Holder to Cytogen.

          (b) Cytogen hereby waives demand and presentment for 
payment, notice of nonpayment, protest and notice of protest, 
diligence, filing suit, and all other notice and promises to 
pay the Holder its costs of collection of all amounts due 
hereunder, including reasonable attorneys' fees.

          (c) In the case of any Event of Default or breach of 
this Note by Cytogen this Note shall continue to bear interest 
after such default or breach at the interest rate otherwise in 
effect hereunder plus 3% per annum (but in any event not in 
excess of the maximum rate of interest permitted by applicable 
law).

     SECTION 8.  RANK
                 ----

          This Note shall be subordinated to currently 
existing senior indebtedness of Cytogen; provided, that from 
and after the date hereof, and for anytime that principal or 
accrued interest shall be outstanding hereunder, Cytogen shall 
not incur any indebtedness for money borrowed which shall rank 
senior to, or pari passu with, this Note without the prior

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consent of the Holder.  Nothing contained herein shall be 
construed as to prevent Cytogen from incurring and paying 
obligations in the ordinary course of business, in accordance 
with past practice.

     SECTION 9.	MISCELLANEOUS

          (a) EIS may assign this Note to its affiliates.  
This Note and all of the provisions hereof shall be binding 
upon and inure to the benefit of the parties hereto and their 
respective successors and assigns; provided, however, that EIS 
and Cytogen shall remain liable for their respective 
obligations hereunder after any such assignment.

          (b) All notices, demands and requests of any kind to 
be delivered to any party in connection with this Agreement 
shall be in writing and shall be deemed to have been duly 
given if personally delivered or if sent by nationally-
recognized overnight courier or by registered or certified 
airmail, return receipt requested and postage prepaid, 
addressed as follows:

               (i) if to Cytogen:

               Cytogen Corporation
               600 College Road East
               Princeton, NJ 08540-5308
               Attn: President

               (ii) if to EIS, to:

               Elan International Services, Ltd.
               102 St. James Court
               Flatts, Smiths Parish
               Bermuda  SL04
               Attention: Director

               with a copy to:

               Brock Silverstein McAuliffe LLC
               Citicorp Center
               153 East 53rd Street 
               New York, New York 10022
               Attention: David Robbins

          Each party, by written notice given to the other in 
accordance with this Section 9(b) may change the address to 
which notices, other communication or documents are to be sent 
to such party.  All notices, other communications or documents 
shall be deemed to have been duly given when received. Any 
such notice or communication shall be deemed to have been 
received (iv) in the case of personal delivery, on the date of 
such delivery, (v) in the case of nationally-recognized 
overnight courier, on the second business day after the date 
when sent and (vi) in the case of mailing, on the fifth 
business day following that day on which the piece of mail 

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containing such communication is posted.  Notice hereunder may 
be given on behalf of the parties by their respective 
attorneys.

(c) This Note may not be changed or terminated 
orally and shall be governed by and construed in accordance 
with the laws of the state of New York, without reference to 
the principles of conflicts of laws thereof.




                      [Signature page follows]

 


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          IN WITNESS WHEREOF, Cytogen and EIS have executed 
this Note on the date first above written.

                               CYTOGEN CORPORATION


                               By: /s/ John E. Bagalay, Jr.
                                   ---------------------------
                                   Name:  John E. Bagalay, Jr.
                                   Title: President and Chief Executive Officer


                               ELAN INTERNATIONAL SERVICES, LTD.


                               By: /s/ Kevin Insley
                                   ---------------------------
                                   Name:  Kevin Insley
                                   Title: President


  

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                              EXHIBIT A

        NOTICE OF ELECTION TO EXERCISE THE CONVERSION RIGHT
        ---------------------------------------------------

Date:

To:    	Cytogen Corporation

From:	  The Holder of the Convertible Promissory Note 
        dated as of August 12, 1998

Re:	    Exercise of the Conversion Right


Pursuant to the terms of the Convertible Promissory Note 
(the "Note") issued by Cytogen Corporation ("Cytogen") to Elan 
International Services, Ltd. ("EIS") as of August 12, 1998, 
specifically Section 3 thereof, the Holder hereby notifies 
Cytogen of its intention to exercise its right of conversion.

Pursuant to Section 3 of the Note, the Holder hereby 
elects to convert the principal and all accrued and unpaid 
interest on the Note for shares of the common stock of 
Cytogen, par value $.01 per share, based upon a conversion 
rate of $2.80 per share.

We have instructed our attorneys to contact Cytogen to 
discuss the timing and documentation of the exchange.


                                         Sincerely,

                                 The Holder

                                 ______________________________


                                 By:___________________________
                                     Name:
                                     Title:


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