8-K

                               Page 1 of 6 pages

                                  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 18, 1998



                           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)



              10070 Barnes Canyon Road, San Diego, California 92121
                    (Address of principal executive offices)



       Registrant's telephone number, including area code: (619) 812-7001











Item 5.  Other Events.

         Final European Approval of OPTISONtm

         On May 18, 1998,  OPTISON,  the  Company's  second-generation  contrast
agent for cardiac ultrasound imaging,  received final marketing authorization by
the European Agency for the Evaluation of Medicinal Products for use in patients
with suspected or known cardiovascular  disease. The authorization covers all 15
member states of the European Union.

         A copy of the  press  release  that the  Company  jointly  issued  with
Mallinckrodt, Inc., on May 19, 1998, is attached to this Report as Exhibit 10.1.
Mallinckrodt, Inc., is the Company's marketing partner for OPTISON in the United
States and most other regions of the world.








                                  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 22, 1998.


           Molecular Biosystems, Inc.



           By       /s/ Gerard A. Wills
                    Gerard A. Wills
                    Vice President, Finance
                      and Chief Financial Officer







                                 Exhibit Index
                                                              Sequentially
     Exhibit         Description                              Numbered Page

     10.1            Press release (May 19, 1998)                  5

EX-10

                                                                   Exhibit 10.1

FOR IMMEDIATE RELEASE

Molecular Biosystems, Inc.
         Robert P. Giargiari, Investor Relations (619) 812-7179
         Patricia Sullivan, Corporate Communications (619) 812-7146
         E-Mail:  IR@mobi.com

Mallinckrodt Inc.
         Media Contacts:   Barbara Abbett (314) 854-5230
                                    Peter Faur (314) 654-5234
                                    E-Mail:  Communications@mkg.com

         Investors Contacts:        Barbara Gould (314) 654-3190
                                    E-Mail: Invest@mkg.com

                  Molecular Biosystems and Mallinckrodt Report
                     Final European Approval of OPTISON(TM)
          Product is first-to-market in Europe; immediate launch planned

         ST. LOUIS, Missouri, and San Diego, Calif., May 19, 1998-Mallinckrodt 
Inc. (NYSE: MKG) and Molecular Biosystems, Inc. (NYSE:MB) ("MBI") today 
announced that OPTISON(TM), the world's first and only commercially available
next-generation cardiac ultrasound contrast imaging agent, has received final
marketing authorization by the European Commission for use in patients with
suspected or known cardiovascular disease.  The authorization covers all 15 
member states of the European Union.

         OPTISON  is the  only  fluorocarbon-based  agent  approved  for  use in
Europe. Mallinckrodt plans to launch OPTISON immediately in Germany, Austria and
the United  Kingdom,  followed by other European  member states pending  certain
pricing approvals.  This initial launch will target a significant portion of the
total European market.

         "We are pleased to be able to bring the benefits of OPTISON to European
patients,"  said  C.  Ray  Holman,  chairman  and  chief  executive  officer  of
Mallinckrodt.  "OPTISON  is being well  received  in the United  States,  and we
believe the European  community  will be equally  accepting of this exciting new
tool for ultrasound cardiac imaging."

         OPTISON has been  available  commercially  in the United  States  since
January 1998 and is being used in nearly 500 U.S. hospitals and cardiology group
practices.  MBI  and  Mallinckrodt  attribute  OPTISON's  early  success  to (1)
outstanding product efficacy;  (2) an excellent safety profile; (3) ease of use;
and (4)  exclusivity  in the  marketplace.  Cardiologists  view the product as a
significant  adjunct to their  diagnostic  capabilities  in  difficult  to image
patients.

         "The approval of OPTISON in Europe gives us the  distinction of having,
once  again,  the first  and only  product  of its kind in a large  and  growing
market," remarked Bobba Venkatadri, president and CEO of MBI. "OPTISON, with its
impressive  safety and  efficacy  profile,  is  setting  the gold  standard  for
contrast  agents in the  United  States,  and we expect no less in the  European
market."

         Molecular Biosystems (NYSE: MB), based in San Diego,  California,  is a
world leader in the development  and  commercialization  of ultrasound  contrast
agents for diagnostic  imaging.  The company's  breakthrough  product,  OPTISON,
enables improved  diagnosis of heart disease through clearer  ultrasound images.
Information  about  MBI  may  be  obtained  via  fax  by  calling   888/329-4007
(toll-free)    or   via   the    internet   by   pointing    your   browser   to
(http://www.mobi.com).

         Based in St. Louis, Mo., Mallinckrodt Inc. has three healthcare
products: group-Imaging, Pharmaceuticals and Respiratory.  The company operates
in more than 100 countries and had fiscal 1997 net sales of $1.9 billion.  The
Mallinckrodt web site address is (www.mallinckrodt.com).

         This news release contains forward-looking statements that involve risk
and  uncertainties.  Among  the  factors  that  could  result  in  a  materially
difference outcome include: the failure of OPTISON(TM) to gain market acceptance
in Europe  or other  markets,  an  adverse  result  in MBI's and  Mallinckrodt's
pending patent  lawsuits,  or an adverse ruling by the PTO in the pending patent
reexaminations:  and other risk  factors  reported  from time to time in MBI and
Mallinckrodt's filings with the Securities Exchange Commission.