UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 4 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP [ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. 1. Name and Address of Reporting Person(s) Hougen, Elizabeth L 10030 Barnes Canyon Road San Diego, CA 92121-2789 2. Issuer Name and Ticker or Trading Symbol Molecular Biosystems, Inc. (MB) 3. I.R.S. Identification Number of Reporting Person, if an entity (Voluntary) 4. Statement for Month/Year 05/00 5. If Amendment, Date of Original (Month/Year) 6. Relationship of Reporting Person(s) to Issuer (Check all applicable) [ ] Director [ ] 10% Owner [X] Officer (give title below) [ ] Other (specify below) Chief Financial Officer 7. Individual or Joint/Group Filing (Check Applicable Line) [X] Form filed by One Reporting Person [ ] Form filed by More than One Reporting Person

Table I Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned ------------------------------------------------------------------------------------------------------------------------------------ 1)Title of Security 2)Trans- 3.Trans- 4.Securities Acquired(A) 5)Amount of 6) 7)Nature of action action or Disposed of (D) Securities Indirect Date Code A Beneficially D Beneficial (Month/ or Owned at or Ownership Day/Year) Code V Amount D Price End of Month I ------------------------------------------------------------------------------------------------------------------------------------ Common Stock 05/09/00 J 11,069 (1) D 20,256 D Direct Table II (PART 1) Derivative Securities Acquired, Disposed of, or Beneficially Owned (Columns 1 through 6) ------------------------------------------------------------------------------------------------------------------------------------ 1)Title of Derivative 2)Conversion 3)Trans- 4)Trans- 5)Number of Derivative 6)Date Exercisable and Security or Exercise action action Securities Acquired (A) Expiration Date Price of Date Code or Disposed of (D) Derivative Security Code V A D Exercisable Expiration ------------------------------------------------------------------------------------------------------------------------------------ ~~Incentive Stock Option (right $0.7188 05/24/00 A 125,000 05/24/01 05/24/10 to buy)~~ Table II (PART 2) Derivative Securities Acquired, Disposed of, or Beneficially Owned (Columns 1,3 and 7 through 11) ------------------------------------------------------------------------------------------------------------------------------------ 1)Title of Derivative 3)Trans- 7)Title and Amount 8)Price 9)Number of 10) 11)Nature of Security action of Underlying of Deri- Derivative Indirect Date Securities vative Securities D Beneficial Amount or Security Beneficially or Ownership Number of Owned at I - Title Shares End of Month ------------------------------------------------------------------------------------------------------------------------------------ ~~Incentive Stock Option (right 05/24/00 Common Stock 125,000 125,000 D Direct to buy)~~ Explanation of Responses: -(1) ~~Option~~Cancellation ~~grants~~of ~~vest~~shares ~~25%~~in ~~per~~satisfaction ~~year~~of ~~over~~tax ~~four years~~liability.

SIGNATURE OF REPORTING PERSON /S/ By: Kevin Helmbacher For: Elizabeth L. Hougen DATE

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