content: UNITED STATES
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D.C. 20549
  
  
  
  
                                      FORM 8-K
  
  
  
                                   CURRENT REPORT
  
  
       Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
  
  
  
            Date of Report (date of earliest event reported): May 3, 1999
  
  
  
                             MOLECULAR BIOSYSTEMS, INC.
               (Exact name of registrant as specified in its charter)
  
  
  
                            Delaware 1-10546 36-30878632
                (State or other juris- (Commission file (IRS employer
              diction of incorporation) number) identification number)
  
  
  
                10030 Barnes Canyon Road, San Diego, California 92121
                      (Address of principal executive offices)
  
  
  
         Registrant's telephone number, including area code: (619) 812-7200
  
  
  
  
  
  
  <PAGE>
  Item 5. Other Events.
  
       Molecular Biosystems, Inc. and Mallinckrodt, Inc. Receive Notice of Lawsuit
  
           On May 5, 1999, Molecular Biosystems, Inc. (the "Company") announced
  that DuPont Pharmaceuticals Company ("DuPont") and ImaRx Pharmaceutical Corp. 
  ("ImaRx") filed a lawsuit in the United States District Court for the District
  of Delaware against MBI and its marketing partner Mallinckrodt, Inc.  The 
  lawsuit alleges that the manufacture and sale of OPTISON(r) infringes 
  U.S. Patent No. 5,547,656 owned by ImaRx and exclusively licensed to DuPont.
  
           A copy of the press release that the Company jointly issued with 
  Mallinckrodt, Inc., on May 5, 1999, is attached to this Report as Exhibit 99.1.
  Mallinckrodt, Inc., is the Company's marketing partner for OPTISON in the
  United States and most other regions of the world.
  
           Statements in this current report on Form 8-K may constitute forward 
  looking statements and are subject to numerous risks and uncertainties.  Among
  the factors that could result in a materially different outcome are:  the 
  failure of OPTISON to gain market acceptance either in the U.S. or other 
  markets; an adverse result in MBI's and Mallinckrodt's pending patent lawsuits,
  including the lawsuit announced by DuPont and ImaRx, or an adverse ruling by 
  the PTO in the pending patent reexaminations; and other risk factors reported
  from time to time in MBI's and Mallinckrodt's filings with the Securities and 
  Exchange Commission.
  
  <PAGE>
                                      Signature
        Pursuant to the requirements of the Securities Exchange Act of 1934,
  the registrant has duly caused this report to be signed on its behalf by the 
  undersigned hereunto duly authorized.
  
             Date:   May 12, 1999
  
  
             Molecular Biosystems, Inc.
  
  
  
             By      /s/ Elizabeth L. Hougen
                        Elizabeth L. Hougen
                    Executive Director, Finance and Chief Financial Officer
  
  
  
  <PAGE>
                                    Exhibit Index
  
  Sequentially
   Exhibit              Description                          Numbered Page
  
    99.1                Press release (May 5, 1999)                5
metadata_documents: [{"type": "8-K", "sequence": "1", "description": "8-K", "secsgml_size_bytes": 3100}]
metadata_filer: {"company-data": {"conformed-name": "MOLECULAR BIOSYSTEMS INC", "cik": "0000719598", "assigned-sic": "2835", "irs-number": "363078632", "state-of-incorporation": "DE", "fiscal-year-end": "0331"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-10546", "film-number": "99618975"}, "business-address": {"street1": "10030 BARNES CANYON RD", "city": "SAN DIEGO", "state": "CA", "zip": "92121-2789", "phone": "6198127001"}, "mail-address": {"street1": "10030 BARNES CANYON ROAD", "city": "SAN DIEGO", "state": "CA", "zip": "92121"}}
text: UNITED STATES
                         SECURITIES AND EXCHANGE COMMISSION
                               Washington, D.C. 20549
  
                                      FORM 8-K
  
                                   CURRENT REPORT
  
       Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
  
            Date of Report (date of earliest event reported): May 3, 1999
  
                             MOLECULAR BIOSYSTEMS, INC.
               (Exact name of registrant as specified in its charter)
  
                            Delaware 1-10546 36-30878632
                (State or other juris- (Commission file (IRS employer
              diction of incorporation) number) identification number)
  
                10030 Barnes Canyon Road, San Diego, California 92121
                      (Address of principal executive offices)
  
         Registrant's telephone number, including area code: (619) 812-7200
  Item 5. Other Events.
  
       Molecular Biosystems, Inc. and Mallinckrodt, Inc. Receive Notice of Lawsuit
  
           On May 5, 1999, Molecular Biosystems, Inc. (the "Company") announced
  that DuPont Pharmaceuticals Company ("DuPont") and ImaRx Pharmaceutical Corp. 
  ("ImaRx") filed a lawsuit in the United States District Court for the District
  of Delaware against MBI and its marketing partner Mallinckrodt, Inc.  The 
  lawsuit alleges that the manufacture and sale of OPTISON(r) infringes 
  U.S. Patent No. 5,547,656 owned by ImaRx and exclusively licensed to DuPont.
  
           A copy of the press release that the Company jointly issued with 
  Mallinckrodt, Inc., on May 5, 1999, is attached to this Report as Exhibit 99.1.
  Mallinckrodt, Inc., is the Company's marketing partner for OPTISON in the
  United States and most other regions of the world.
  
           Statements in this current report on Form 8-K may constitute forward 
  looking statements and are subject to numerous risks and uncertainties.  Among
  the factors that could result in a materially different outcome are:  the 
  failure of OPTISON to gain market acceptance either in the U.S. or other 
  markets; an adverse result in MBI's and Mallinckrodt's pending patent lawsuits,
  including the lawsuit announced by DuPont and ImaRx, or an adverse ruling by 
  the PTO in the pending patent reexaminations; and other risk factors reported
  from time to time in MBI's and Mallinckrodt's filings with the Securities and 
  Exchange Commission.
  Signature
        Pursuant to the requirements of the Securities Exchange Act of 1934,
  the registrant has duly caused this report to be signed on its behalf by the 
  undersigned hereunto duly authorized.
  
             Date:   May 12, 1999
  
             Molecular Biosystems, Inc.
  
             By      /s/ Elizabeth L. Hougen
                        Elizabeth L. Hougen
                    Executive Director, Finance and Chief Financial Officer
  Exhibit Index
  
  Sequentially
   Exhibit              Description                          Numbered Page
  
    99.1                Press release (May 5, 1999)                5