<PAGE>

                              UNITED STATES
                    SECURITIES AND EXCHANGE COMMISSION
                          WASHINGTON, D.C. 20549

                                SCHEDULE 13G

    INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO
                          (Amendment No.       )(1)
                                         ------

                          Harvard Bioscience, Inc.
--------------------------------------------------------------------------------
                              (Name of Issuer)

                   Common Stock, par value $.01 per share
--------------------------------------------------------------------------------
                       (Title of Class of Securities)

                                416906 10 5
                     ----------------------------------
                              (CUSIP Number)

                            December 12, 2000
--------------------------------------------------------------------------------
               (Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this 
Schedule is filed:

     / / Rule 13d-1(b)

     / / Rule 13d-1(c)

     /x/ Rule 13d-1(d)

----------

  (1)The remainder of this cover page shall be filled out for a reporting 
person's initial filing on this form with respect to the subject class of 
securities, and for any subsequent amendment containing information which 
would alter the disclosures provided in a prior cover page.

   The information required in the remainder of this cover page shall not 
be deemed to be "filed" for the purpose of Section 18 of the Securities 
Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that 
section of the Act but shall be subject to all other provisions of the Act 
(however, see the Notes).

                       (Continued on the following pages)

                              (Page 1 of 5 Pages)


<PAGE>

                                 SCHEDULE 13G
CUSIP No. 416906105                                          Page 2 of 5 Pages
          ---------

-------------------------------------------------------------------------------
 (1) Names of Reporting Persons. David Green
     I.R.S. Identification Nos. of above persons (entities only).

     S.S.N. 547-81-3161
-------------------------------------------------------------------------------
 (2) Check the Appropriate Box if a Member   (a)  / /
     of a Group (See Instructions)           (b)  / /
-------------------------------------------------------------------------------
 (3) SEC Use Only

-------------------------------------------------------------------------------
 (4) Citizenship or Place of Organization
     The Commonwealth of Massachusetts, U.S.A.
-------------------------------------------------------------------------------
 Number of Shares             (5) Sole Voting Power
 Beneficially                     3,306,936
 Owned by                    --------------------------------------------------
 Each Reporting               (6) Shared Voting Power
 Person With:                     None
                             --------------------------------------------------
                              (7) Sole Dispositive Power
                                  3,306,936
                             --------------------------------------------------
                              (8) Shared Dispositive Power
                                  None
-------------------------------------------------------------------------------
 (9) Aggregate Amount Beneficially Owned by Each Reporting Person
     3,306,936 Shares of Common Stock
-------------------------------------------------------------------------------
(10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See
     Instructions)        / /
-------------------------------------------------------------------------------
(11) Percent of Class Represented by Amount in Row (9)
     12.9%
-------------------------------------------------------------------------------
(12) Type of Reporting Person *(See Instructions)
     IN
-------------------------------------------------------------------------------



<PAGE>

                            STATEMENT ON SCHEDULE 13G

ITEM 1.

     (a) Name of Issuer

         HARVARD BIOSCIENCE, INC.

     (b) Address of Issuer's Principal Executive Offices

         84 OCTOBER HILL ROAD
         HOLLISTON, MASSACHUSETTS 01746

ITEM 2.

     (a) Name of Person Filing

         DAVID GREEN

     (b) Address of Principal Business Office or, if none, Residence

         84 OCTOBER HILL ROAD
         HOLLISTON, MASSACHUSETTS 01746


     (c) Citizenship

         THE COMMONWEALTH OF MASSACHUSETTS, U.S.A.

     (d) Title of Class of Securities

         COMMON STOCK, PAR VALUE $.01 PER SHARE

(e)      CUSIP Number

         416906 10 5

ITEM 3. IF THIS STATEMENT IS FILED PURSUANT TO SECTIONS 240.13D-1(b) OR
240.13D-2(b) OR (c), CHECK WHETHER THE PERSON FILING IS A:

        NOT APPLICABLE

     (a) [ ] Broker or dealer registered under section 15 of the Act 
         (15 U.S.C. 78o).

     (b) [ ] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

     (c) [ ] Insurance company as defined in section 3(a)(19) of the Act 
         (15 U.S.C. 78c).

     (d) [ ] Investment company registered under section 8 of the Investment
         Company Act of 1940 (15 U.S.C. 80a-8).

     (e) [ ] An investment adviser in accordance with 
         section 240.13d-1(b)(1)(ii)(E);


                                  Page 3 of 5



<PAGE>


     (f) [ ] An employee benefit plan or endowment fund in accordance
         with section 240.13d-1(b)(1)(ii)(F);

     (g) [ ] A parent holding company or control person in accordance
         with section 240.13d-1(b)(1)(ii)(G);

     (h) [ ] A savings associations as defined in Section 3(b) of the Federal
         Deposit Insurance Act (12 U.S.C. 1813);

     (i) [ ] A church plan that is excluded from the definition of an investment
         company under section 3(c)(14) of the Investment Company Act of 1940 
         (15 U.S.C. 80a-3);

     (j) [ ] Group, in accordance with section 240.13d-1(b)(1)(ii)(J).

ITEM 4. OWNERSHIP

     (a) Amount beneficially owned: 3,306,936

     (b) Percent of class: 12.9%

     (c) Number of shares as to which the person has:

          (i) Sole power to vote or to direct the vote: 3,306,936

          (ii) Shared power to vote to direct the vote: NONE

          (iii) Sole power to dispose or to direct the disposition of: 3,306,936

          (iv) Shared power to dispose or to direct the disposition of: NONE

ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS

        NOT APPLICABLE

If this statement is being filed to report the fact that as of the date hereof
the reporting person has ceased to be the beneficial owner of more than five
percent of the class of securities, check the following [ ].

ITEM 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON.

        NOT APPLICABLE

ITEM 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE
SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY.

        NOT APPLICABLE

ITEM 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP

        NOT APPLICABLE


                                  Page 4 of 5



<PAGE>


ITEM 9. NOTICE OF DISSOLUTION OF GROUP

        NOT APPLICABLE

ITEM 10. CERTIFICATION

                                    SIGNATURE


After reasonable inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.

                                FEBRUARY 8, 2001
                         -------------------------------
                                      Date


                                /S/ DAVID GREEN
                         -------------------------------
                                    Signature


                                   DAVID GREEN
                         -------------------------------
                                   Name/Title




                                  Page 5 of 5