EXHIBIT 4.20

                  WARRANT TO PURCHASE SHARES OF COMMON STOCK OF
                         AMERICAN BIO MEDICA CORPORATION

      Warrant No. 001                                    Dated: October 28, 2000
      Amend No. 5

      This certifies that Steven Grodko (the "Holder"),  for value received,  is
entitled,  subject to the terms set forth below,  to purchase  from AMERICAN BIO
MEDICA  CORPORATION,  a New York  Corporation (the  "Company"),  400,000,  (Four
hundred  thousand)  fully paid and  nonassessable  Common  Shares (the  "Warrant
Shares") of the Company,  par value $.01 per share (the "Stock"),  at a price of
$0.95 per share (the "Stock  Purchase  Price") at any time but not earlier  than
that  Commencement Date (as defined below) or later than 5:00 pm (New York Time)
on the  Expiration  Date (as defined below) upon surrender to the Company at its
principal  office at 122 Smith  Road,  Kinderhook,  New York  12106,  Attention:
Corporate  Secretary  (or at such other  location  as the Company may advise the
Holder in writing) of this Warrant  properly  endorsed with the form of Exercise
Notice  attached  hereto  duly  completed  and  signed  upon  payment in cash or
cashier's  check of the aggregate  Stock Purchase Price for the number of shares
for which the  Warrant is being  exercised  determined  in  accordance  with the
provisions  hereof.  The Stock  Purchase  Price and the number of Warrant Shares
purchasable hereunder are subject to adjustment as provided in Section 3 of this
Warrant.  This Warrant and all rights hereunder,  to the extent not exercised in
the manner set forth  herein  shall  terminate  and become  null and void on the
Expiration Date (as defined below).  "Commencement  Date" shall mean the date of
this  Warrant.  "Expiration  Date"  shall  mean  the  sixth  anniversary  of the
Commencement Date.

      This  Warrant is subject to the following terms and conditions:

      1.    Exercise; Issuance of Certificates; Payment for Warrant Shares.

      (a) This Warrant is  exercisable by payment of the Stock Purchase Price by
cash payment, certified check or wire transfer, in the manner set forth above at
the option of the Holder at any time but not earlier than the Commencement  Date
or  later  than  5:00 pm (New  York  Time) on the  Expiration  Date for all or a
portion of the shares of Stock subject to this Warrant.  The Company agrees that
the Warrant  Shares  purchased  under this Warrant shall be and are deemed to be
issued  to the  Holder  as the  record  owner of such  shares as of the close of
business  on the date on which  this  Warrant  shall have been  surrendered  and
payment made for such shares (unless the Conversion Right is exercised). Subject
to the provisions of Section 2, certificates for the Warrant Shares so purchased
shall  be  delivered  to the  Holder  by the  Company's  transfer  agent  at the
Company's   expense  within  a  reasonable  amount  of  time  after  the  rights
represented by this Warrant have been  exercised.  The stock  certificate(s)  so
delivered  shall be  registered  in the name of the Holder or such other name as
shall be  designated  by the Holder,  subject to the  limitations  contained  in
Section 2. If, upon  exercise of this  Warrant,  fewer than all of the shares of
Stock  evidenced by this Warrant are purchased  prior to the Expiration  Date of
this Warrant, one or more new warrants  substantially in the form of, and on the
terms of,  this  Warrant  will be issued for the  remaining  number of shares of
Stock not purchased upon exercise of this Warrant.

                                                                               1
                                  Exhibit 4.20



      (b) Subject to the mutual agreement of the Company and the Holder, in lieu
of the payment of the Stock Purchase  Price,  the Holder may require the Company
to  convert  this  Warrant  into  shares of Stock  (the  "Conversion  Right") as
provided for in this Section 1(b).  Upon exercise of the Conversion  Right,  the
Company shall deliver to the Holder (without payment by the Holder of any of the
Stock  Purchase  Price)  that  number  of share of Stock  equal to the  quotient
obtained  by dividing  (x) the value of the  Warrant at the time the  Conversion
Right is exercised (determined by subtracting the aggregate Stock Purchase Price
in effect  immediately  prior to the exercise of the  Conversion  Right from the
aggregate Market Value (as defined in Section 1(d) below) for the Warrant Shares
immediately  prior to the  exercise of the  Conversion  Right) by (y) the Market
Value.

      (c) The Conversion  Right may be exercised by the Holder by delivering the
Warrant  Certificate  with a duly executed  Exercise Notice in the form attached
hereto with the conversion section completed by the Company.

      (d) For the sole purpose of determining the number of Warrant Shares which
shall be delivered to the Holder by the Company pursuant to the Conversion Right
as ser forth in Section 1(b) above,  "Market Value" shall mean the average daily
closing price of a share of the Stock listed on the Nasdaq  SmallCap  Market (or
such other  exchange or quotation  system on which the Stock may then be listed)
for the ten (10)  consecutive  days of trading  ending on the third business day
immediately  preceding the date of exercise of such Conversion  Right, or in the
event  the  Stock  is not  then  publicly  traded,  the  Market  Value  shall be
determined in good faith by the Company and the Holder. In the event the Parties
are unable to agree upon the Market Value within thirty (30) days of the date of
exercise of the  Conversion  Right,  the Market Value shall be  determined  by a
nationally  recognized  investment  banking firm by lot from two (2)  investment
baking firms chosen by the Company and two (2)  investment  banking firms chosen
by the Holder, none of which shall have been engaged by either Party within five
(5) years prior to the date of selection.

      2. Shares to be fully paid; Reservation of Shares.

      The  Company  covenants  and agrees  that the Warrant  Shares  will,  upon
issuance,  be duly authorized,  validly issued,  fully paid and nonasessable and
free from all preemptive  rights of any stockholder and free of all taxes (other
than income taxes which may be applicable to the Holder), liens and charges with
respect to the issuance thereof.  The Company covenants that it will reserve and
keep  available a  sufficient  number of shares of its  authorized  but unissued
Stock for such exercise. The Company will take all such reasonable action as may
be  necessary  to  assure  that such  shares of Stock may be issued as  provided
herein  without  violation  of  any  applicable  law  or  regulation,  or of any
requirement of any domestic  securities  exchange or automated  quotation system
upon which the Stock may be listed.

      3. Adjustment of Stock Purchase Price and Number of Shares.

      The Stock  Purchase  Price and the number of shares  purchasable  upon the
exercise of this Warrant,  shall be subject to adjustment from time to time upon
the occurrence of certain events described in this Section 3.

      3.1  Subdivision or Combination of Stock and Stock  Dividend.  In case the
Company  shall at any time  subdivide  its  outstanding  shares of Stock  into a
greater  number of shares or declare a dividend upon its Stock payable solely in
shares of Stock,  the Stock Purchase Price in effect  immediately  prior to such
subdivision of declaration shall be proportionately  reduced,  and the number of
shares issuable upon exercise of the Warrant shall be proportionately increased.
Conversely,  in case the  outstanding  shares of Stock of the  Company  shall be
combined into a smaller  number of shares,  the Stock  Purchase  Price in effect
immediately prior to such combination shall be  proportionately  increased,  and
the  number  of  shares   issuable   upon  exercise  of  the  Warrant  shall  be
proportionately reduced.

                                                                               2
                                  Exhibit 4.20



      3.2 Anti-dilution Protection. If at any time prior to the exercise of this
Warrant in full,  the Company shall issue or sell any Common Stock or securities
(the "Additional  Securities") convertible in Common Stock for consideration per
share (the "Adjusted Per Share Price") (in cash,  property or other assets) less
than the Stock Purchase Price on the date of such issuance or sale of Additional
Securities,  the  Stock  Purchase  Price  in  effect  immediately  prior to such
issuance  or sales shall be reduced to the  Adjusted  Per Share  Price,  and the
number  of  Warrants   issuable   upon   exercise  of  this  Warrant   shall  be
proportionately  increased  such that the  aggregate  number of  Warrant  Shares
issuable  under this  Warrant  multiplied  by the Adjusted Per Share Price shall
equal  [$905,619]  adjusted for any prior  exercises.  The foregoing  adjustment
shall not be made in the event the Company issues or sells Additional Securities
upon exercise of outstanding  options or warrants as of the Commencement Date or
options  reserved for issuance under the Company's  stock option plans as of the
Commencement  Date. The anti-dilution  protection  contained herein shall not be
applicable  to any shares  already  outstanding  pursuant to an exercise of this
Warrant.

      3.3 Notice of Adjustment.  Promptly after adjustment of the Stock Purchase
Price of any increase or decrease in the number of shares  purchasable  upon the
exercise of this Warrant,  the Company  shall give written  notice  thereof,  by
first class mail, postage prepaid, addressed to the Holder at the address of the
Holder as shown on the books of the  Company.  The notice shall be signed by and
authorized  officer of the  Company and shall  state the  effective  date of the
adjustment and the Stock Purchase Price  resulting from such  adjustment and the
increase or decrease,  if any, in the number of share  purchasable at such price
upon the exercise of this Warrant, setting forth in reasonable detail the method
of calculation and the fact upon which such calculation is based.

      3.4 Other Notices. If at any time:

      (a)   the Company shall declare any cash dividend upon its Stock;

      (b)   the Company  shall  declare any dividend  upon its Stock  payable in
            stock (other than a dividend  payable  solely in shares of Stock) or
            make any special  dividend or other  distribution  to the holders of
            its Stock;

      (c)   there  shall be any  consolidation  or  merger of the  Company  with
            another  corporation,  or a sale of all or substantially  all of the
            Company's assets to another corporation; or

      (d)   there shall be a voluntary or involuntary  dissolution,  liquidation
            or winding-up of the Company.

then, in any one or more of said cases,  the Company shall give, by certified or
registered  mail,  postage prepaid,  addressed to the registered  Holder of this
Warrant at the address of the Holder as shown on the books of the  Company,  (i)
at least ten (10) days  prior  written  notice of the date on which the books of
the  Company  shall  close  or a  record  shall  be  taken  for  such  dividend,
distribution  or  subscription  rights  or for  determining  rights to vote with
respect of any such  dissolution,  liquidation or winding-up,  (ii) at least ten
(10) days  prior  written  notice of the date on which the books of the  Company
shall close or a record shall be taken for determining rights to vote in respect
of any such reorganization, reclassification, consolidation, merger or sale, and
(iii) in the case of any such reorganization,  reclassification,  consolidation,
merger,  sale,  dissolution,  liquidation or winding-up,  at least ten (10) days
written  notice of the date when the same shall take place.  Any notice given in
accordance  with  clause (i) above shall also  specify,  in the case of any such
dividend, distribution, or option rights, the date on which the holders of Stock
shall be entitled  thereto.  Any notice  given in  accordance  with clause (iii)
above  shall  also  specify  the date on which  the  holders  of Stock  shall be
entitled to exchange their Stock for  securities or other  property  deliverable
upon  such  reorganization,   reclassification,   consolidation,   merger,  sale
dissolution, liquidation or winding-up, as the case may be.

                                                                               3
                                  Exhibit 4.20



      3.5 Changes in Stock.  In case at any time prior to the  Expiration  Date,
the Company shall be a party to any transaction (including without limitation, a
merger, consolidation,  sale of all or substantially all of the Company's assets
or  recapitalization  of the Stock) in which the  previously  outstanding  Stock
shall be changed into or exchanged  for  different  securities of the Company or
common  stock or other  securities  of another  corporation  or  interests  in a
non-corporate  entity or other  property  (including  cash) or the Company shall
make a  distribution  of its shares,  other than regular  cash  dividends on its
outstanding  stock,  or any  combination  of any of  the  foregoing  (each  such
transaction  being herein called the  "Transaction" and the date of consummation
of the  Transaction  being herein  called the  `Consummation  Date",  then, as a
condition of the consummation of the Transaction, lawful and adequate provisions
shall be made so that each Holder,  upon exercise hereof at any time on or after
the  Consummation  Date,  shall be entitled to receive,  and this Warrant  shall
thereafter  represent the right to receive,  in lieu of Stock issuable upon such
exercise  prior to the  Consummation  Date,  the highest amount of securities or
other  property  to which the Holder  would  actually  have been  entitled  as a
stockholder upon the consummation of the Transaction if the Holder had exercised
such Warrant  immediately prior thereto.  The provision of the Section 3.5 shall
similarly apply to successive Transactions.

      4. Investment Representations.

      By receipt of this Warrant, and by its execution, the Holder represents to
the Company the following:

      (a) the Holder  understands that this Warrant and any Stock purchased upon
its exercise are  securities,  the issuance of which  requires  compliance  with
federal and state securities laws;

      (b) the Holder is aware of the  Company's  business  affairs and financial
condition and has acquired sufficient  information about the Company to reach an
informed and knowledgeable decision to acquire this Warrant;

      (c) the Holder is acquiring  this Warrant for  investment  in the Holder's
own account only and not with a view to, or for resale in connection  with,  any
"distribution"  thereof  within the meaning of the  Securities  Act of 1933,  as
amended (the "Act"); and

      (d) the Holder acknowledges and understands that the securities constitute
"restricted  securities" under the Act and must be held indefinitely unless they
are subsequently registered under the Act or an exemption from such registration
is available.

      5. Issue Tax.  The issuance of  certificates  for shares of Stock upon the
exercise  of the  Warrant  shall be made  without  charge  to the  Holder of the
Warrant  for any issue  tax in  respect  thereof;  provided,  however,  that the
Company  shall not be required to pay any tax which may be payable in respect of
any transfer  involved in the issuance and delivery of any certificate in a name
other than that of the then Holder of the Warrant being exercised.

      6.  No  Voting  or  Dividend  Rights;  Limitation  on  Liability.  Nothing
contained in this  Warrant  shall be  construed  as  conferring  upon the Holder
hereof the right to vote or to consent or to receive  notice as a stockholder in
respect of meetings of stockholders for the election or directors of the Company
or any other matters or any rights  whatsoever as a stockholder  of the Company.
In  addition,  if the Holder of the Warrant  does not  exercise  this Warrant or
convert this Warrant  pursuant to Section 1(b) above prior to the  occurrence of
an event described above,  except as provided in Section 3.1 and 3.5, the Holder
shall not be entitled to receive the  benefits  accruing to existing  holders of
the Stock  pursuant to such an event.  No dividends or interest shall be payable
or accrued in respect of this Warrant or the interest  represented hereby or the
shares  purchasable  hereunder  until, and only to the extent that, this Warrant
shall have been exercised.  No provisions  hereof, in the absence of affirmative
action by the Holder to purchase shares of Stock, and no mere enumeration herein
of the  rights  or  privileges  of the  Holder  hereof,  shall  give rise to any
liability of the Holder for the Stock  Purchase Price or as a stockholder of the
Company whether such liability is asserted by the Company or by its creditors.

                                                                               4
                                  Exhibit 4.20



      7.  Restrictions  on  Transferability   of  Securities;   Compliance  with
Securities Act.

      7.1 Restrictions on  Transferability.  This Warrant and the Warrant Shares
shall not be transferable in the absence of the  effectiveness of a registration
statement  with  respect  to such  securities  under  the Act,  or an  exemption
therefrom.  This Warrant and the Warrant Shares may be transferred in any manner
of compliance with applicable law.

      7.2  Restrictive   Legend.   In  the  absence  of  the   effectiveness  of
registration under the Act, or an exemption therefrom as contemplated by Section
7.1, each  certificate  representing  the Warrant Shares or any other securities
issued in respect of the Warrant  Shares upon any stock split,  stock  dividend,
recapitalization,  merger,  consolidation or similar event,  shall be stamped or
otherwise  imprinted  with a  legend  substantially  in the  following  form (in
addition to any legend required under applicable state securities laws):

      THE  SECURITIES  REPRESENTED  HEREBY  HAVE NOT BEEN  REGISTERED  UNDER THE
      SECURITIES ACT OF 1933, AS AMENDED ("ACT"), NOR UNDER ANY STATE SECURITIES
      LAWS  AND  NEITHER  THE  SECURITIES  NOR  ANY  INTEREST   THEREIN  MAY  BE
      TRANSFERRED,   PLEDGED,  OR  OTHERWISE  DISPOSED  OF  IN  THE  ABSENCE  OF
      REGISTRATION OR AN EXEMPTION THEREFROM UNDER SAID ACT OR SUCH LAWS AND THE
      RULES AND REGULATIONS THEREUNDER.

      8.  Modification and Waiver.  This Warrant and any provision hereof may be
changed,  waived,  discharged  or  terminated  only be an  instrument in writing
signed by the party against which enforcement of the same is sought.

      9. Notices. Any notice, request or other document required or permitted to
be given or delivered to the Holder  hereof or the Company shall be delivered or
shall be sent by certified or registered mail,  postage prepaid,  to each Holder
at its  address as shown on the books of the  Company  or to the  Company at the
address indicated therefore in the first paragraph of this Warrant.

      10.  Descriptive  Headings and Governing Law. The descriptive  headings of
the several sections and paragraphs of this Warrant are inserted for convenience
only  and do not  constitute  a part of this  Warrant.  This  Warrant  shall  be
construed and enforced in accordance  with,  and the rights of the Parties shall
be governed  by, the laws of the State of New Jersey  without  reference  to the
principles of conflicts of law.

      11.  Lost  Warrants or Stock  Certificates.  The  Company  represents  and
warrants to the Holder that upon receipt of evidence reasonably  satisfactory to
the Company of the loss,  theft,  destruction  or  mutilation  of any Warrant or
stock certificate  representing Warrant Shares and in the case of any such loss,
theft,  destruction  or  mutilation,  upon  receipt  of  an  indemnity  and,  if
requested,  bond reasonably  satisfactory to the Company,  or in the case of any
such  mutilation,  upon  surrender  and  cancellation  of such  Warrant or stock
certificate,  the Company, at its expense will make and deliver a new Warrant or
stock  certificate,  or like tenor,  in lieu of the lost,  stolen,  destroyed or
mutilated Warrant or stock certificate.

                                                                               5
                                  Exhibit 4.20



      12. Fractional  Shares. No fractional shares shall be issued upon exercise
of this Warrant.  The Company shall, in lieu of issuing any fractional share pay
the Holder  entitled  to such  fraction  a sum of cash equal to the fair  market
value of any such  fractional  interest as it shall appear on the public market,
or if there is not public  market for such shares,  then as shall be  reasonably
determined by the Company.

IN WITNESS  WHEREOF,  the Company has caused this  Warrant to be executed by its
officer, thereunto duly authorized as of the date first written above.

                                               AMERICAN BIO MEDICA CORPORATION

                                               By: /s/ Melissa A. Decker
                                                   --------------------------
                                                   Name: Melissa A. Decker
                                                   Title: Corporate Secretary

                                               By: /s/ Keith E. Palmer
                                                   --------------------------
                                                   Name: Keith E. Palmer
                                                   Title: CFO & Director

                                                                               6
                                  Exhibit 4.20



                             FORM OF EXERCISE NOTICE
              (To be signed and delivered upon exercise of Warrant)

AMERICAN BIO MEDICA CORPORATION
122 Smith Road
Kinderhook, New York 12106

      The  undersigned,  the Holder of the within Warrant  (Warrant  Certificate
Number 001,  Amend No. 5),  hereby  irrevocably  elects to exercise the purchase
right  represented by such Warrant for, and to purchase  thereunder,  __________
Common Shares,  par value $0.01 per share (the "Stock"),  of AMERICAN BIO MEDICA
CORPORATION (the "Company"),  and subject to the following  paragraph,  herewith
makes payment of __________  Dollars  ($__________)  therefore and requests that
the  certificate(s)  for such shares be issued in the name of, and delivered to,
__________ whose address is __________.

      The  undersigned  does/does  not (circle  one) request the exercise of the
within Warrant  pursuant to the "Conversion  Right" set forth in Section 1(b) of
the Warrant.

DATED:
      ---------------------
                                         ---------------------------------------
                                         (Signature must conform in all respects
                                         to name of Holder as specified on the
                                         face of the Warrant)

- ---------------------------

- ---------------------------              (Address)

                                                                               7
                                  Exhibit 4.20