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                                                                  EXHIBIT 10.33a


             FIRST AMENDMENT TO CONVERTIBLE NOTE PURCHASE AGREEMENT

         FIRST AMENDMENT, dated as of December 14, 2000 (this "First
Amendment"), to the Convertible Note Purchase Agreement, dated as of April 28,
2000 (the "Note Purchase Agreement"), by and among Bio-Plexus, Inc., a
Connecticut corporation (the "Company"), the Purchasers listed on Exhibit A
thereto, and Appaloosa Management L.P., as Collateral Agent.

                                   WITNESSETH:

         WHEREAS, the Company has issued the Notes to the Purchasers; and

         WHEREAS, in connection with the issuance of the Notes the Company
presented certain operating forecasts in the second revision to its Five Year
Business Plan, dated January 12, 2000 (the "Business Plan"), upon which
Appaloosa relied in setting financial covenants in the Note Purchase Agreement;
and

         WHEREAS, Appaloosa subsequently agreed to suspend such financial
covenant requirements until December 31, 2000 to allow sufficient time for the
Company to hire a new chief executive officer and revise the Business Plan; and

         WHEREAS, the Company's revised Business Plan and the other projections
presented by the Company to Appaloosa since the Closing require that the
financial covenants set forth in the Note Purchase Agreement be revised to more
accurately reflect the revised Business Plan and projections; and

         WHEREAS, the Company desires to amend the financial covenants in the
Note Purchase Agreement for the periods extending beyond December 31, 2000;

         NOW, THEREFORE, in consideration of the premises and mutual covenants
contained herein, the Company, the Purchasers, and the Collateral Agent hereby
agree as follows:

         1. Defined Terms. Unless otherwise defined herein, capitalized terms
which are defined in the Note Purchase Agreement are used herein as therein
defined.

         2. Amendment to the Note.

                  (a) Subsection 6.15 of the Note Purchase Agreement is amended
by deleting the paragraph in its entirety and substituting in lieu therefor the
following:

                  The Company shall maintain the financial covenants specified
in Schedule 6.15.

                  (b) Schedule 6.15 of the Note Purchase Agreement is amended by
deleting the first two charts in their entirety and substituting in lieu
therefor the following charts:
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<TABLE>
<CAPTION>
                                          Minimum (Maximum) Operating Profit     Minimum (Maximum) Operating Profit
                 Date                    (Loss) for three-month period ending      (Loss) for twelve-month period
                                                   on date indicated                  ending on date indicated
<S>                                      <C>                                     <C>
          September 30, 1999                              N/A                                    N/A
           December 31, 1999                              N/A                                    N/A
            March 31, 2000                                N/A                                    N/A
             June 30, 2000                                N/A                                    N/A
          September 30, 2000                              N/A                                    N/A
           December 31, 2000                         ($1,622,000)                           ($1,622,000)*
            March 31, 2001                           ($1,391,000)                          ($3,013,000)**
             June 30, 2001                           ($1,011,000)                          ($4,024,000)***
          September 30, 2001                          ($764,000)                            ($4,788,000)
           December 31, 2001                          ($150,000)                            ($3,316,000)
            March 31, 2002                             $450,000                             ($1,475,000)
             June 30, 2002                             $550,000                                $86,000
          September 30, 2002                           $600,000                              $1,450,000
           December 31, 2002                           $600,000                              $2,200,000
            March 31, 2003                            $1,000,000                             $2,750,000
             June 30, 2003                            $1,250,000                             $3,450,000
          September 30, 2003                          $1,500,000                             $4,350,000
           December 31, 2003                          $1,650,000                             $5,400,000
  March 31, 2004 and the last day of
   each calendar quarter thereafter                   $1,700,000                             $6,500,000
</TABLE>

         *        Represents the trailing 3-month period.

         **       Represents the trailing 6-month period.

         ***      Represents the trailing 9-month period.

<TABLE>
<CAPTION>
                                            Minimum Product Sales       Minimum Product Sales
                                           Revenue for three-month     Revenue for twelve-month
                        Date              period ending on the date     period ending on date
                                                  indicated                   indicated
<S>                                       <C>                          <C>
                  December 31, 1999                  N/A                         N/A
                   March 31, 2000                    N/A                         N/A
                    June 30, 2000                    N/A                         N/A
                 September 30, 2000                  N/A                         N/A
                  December 31, 2000               $1,141,000                 $1,141,000*
                   March 31, 2001                 $1,227,000                 $2,368,000**
                    June 30, 2001                 $1,884,000                $4,252,000***
                 September 30, 2001               $2,352,000                  $6,604,000
                  December 31, 2001               $2,921,000                  $8,384,000
                   March 31, 2002                 $4,000,000                 $11,157,000
                    June 30, 2002                 $4,500,000                 $13,773,000
</TABLE>

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<TABLE>
<CAPTION>
                                            Minimum Product Sales       Minimum Product Sales
                                           Revenue for three-month     Revenue for twelve-month
                        Date              period ending on the date     period ending on date
                                                  indicated                   indicated
<S>                                       <C>                          <C>
                 September 30, 2002               $5,000,000                 $16,421,000
                  December 31, 2002               $5,500,000                 $19,000,000
                   March 31, 2003                 $6,000,000                 $21,000,000
                    June 30, 2003                 $6,500,000                 $23,000,000
                 September 30, 2003               $7,000,000                 $25,000,000
                  December 31, 2003               $7,500,000                 $27,000,000
               March 31, 2004 and the
               last day of each calendar
               quarter thereafter                 $8,500,000                 $32,500,000
</TABLE>

         *        Represents the trailing 3-month period.
         **       Represents the trailing 6-month period.
         ***      Represents the trailing 9-month period.

                  (c) Subsection 6.20 of the Note Purchase Agreement is amended
by deleting clause (e) thereof in its entirety and substituting in lieu
therefor:

                           (e) upon any Holder's request from time to time, such
                           other information (including financial statements,
                           monthly computation of profit and loss, and any other
                           computations) relating to the performance of the
                           provisions of this Agreement and the affairs of the
                           Company and any of its Subsidiaries.

                  (d) Subsection 6.33 of the Note Purchase Agreement is amended
by adding the following text after the final sentence thereof:

                           The Company shall not materially alter or embark upon
                           (other than preliminary non-binding discussions) any
                           new strategic initiatives as a part of its business
                           plan or otherwise, which strategic initiatives shall
                           include, but not be limited to, joint ventures,
                           strategic alliances, licensing agreements,
                           acquisitions, and partnerships of any kind (other
                           than distribution, supply and other similar
                           agreements entered into in the ordinary course of
                           business on commercially reasonable terms), without
                           the express consent of the Collateral Agent.

                  (e) Schedule 6.34 of the Note Purchase Agreement is amended by
adding the following text after the final sentence thereof:

                           Performance Covenants for the Development and Sale of
                           Winged Sets for Blood Collection:

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                                    The Company shall meet the following
                                    milestones on the dates set forth below with
                                    respect to its Winged Set for Blood
                                    Collection product:

                           (i) Complete installation and start-up of a pilot
                           production line by November 30, 2000;

                           (ii) Produce a minimum 15,000 units of pre-launch
                           Winged Set product samples on the pilot production
                           line by January 31, 2001;

                           (iii) Complete installation and start-up of an
                           automated production line by March 31, 2001; and

                           (iv) Begin commercial sale of the Winged Set product
                           by April 2, 2001 and have shipped a minimum of
                           100,000 units of the Winged Set product for
                           commercial sale (which excludes any sale to an
                           Affiliate or to any other Person on a non-arms length
                           basis) by June 30, 2001.

                  (f) Subsection 11.1 of the Note Purchase Agreement is amended
by deleting the definition of "Product Sales Revenues" in its entirety and
substituting in lieu therefor the following definition:

                           "Product Sales Revenues" shall mean all revenues
                           generated by the Company from the sale of medical
                           products manufactured by the Company (excluding, for
                           the avoidance of doubt, any equipment or other
                           machinery sold or licensed to any Person for the
                           manufacture of any such medical products) calculated
                           in accordance with GAAP.

         3. Representations and Warranties. The Company represents and warrants
that the representations and warranties set forth in Section 2 of the Note
Purchase Agreement are true and complete on and as of the date hereof as if made
on the date hereof (or, if any such representation or warranty is expressly
stated to have been made as of a specific date, as of such specific date). The
Company represents and warrants that as of the date hereof and, after giving
effect to this First Amendment and the transactions contemplated hereby, no
Default or Event of Default has occurred and is continuing. The Company
represents that the execution and delivery of this First Amendment by the
Company and the performance by it of the transactions contemplated hereby have
been duly authorized by all requisite corporate proceedings on the part of the
Company.

         4. Effectiveness. The First Amendment shall become effective as of the
date upon which the Collateral Agent receives the counterpart of this First
Amendment duly executed by the Company.

         5. Continuing Effect of the Transaction Documents. This First Amendment
shall not constitute an amendment of any other provisions of the Note Purchase
Agreement or any other Transaction Documents not expressly referred to herein
and shall not be construed as a waiver or consent to any further or future
action on the part of the Company that would require a waiver or consent of the
Purchasers. Except as expressly amended hereby, the provisions of the Note

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Purchase Agreement and the other Transaction Documents are and shall remain in
full force and effect. In the event there is any conflict between the terms of
the Note Purchase Agreement and any other Transaction Document, the terms of the
Note Purchase Agreement shall govern.

         6. Counterparts. This First Amendment may be executed by the parties
hereto in any number of separate counterparts, each of which shall be deemed to
be an original, and all of which taken together shall be deemed to constitute
one and the same instrument.

         7. GOVERNING LAW. THIS FIRST AMENDMENT SHALL BE GOVERNED BY, AND
CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

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         IN WITNESS WHEREOF, the parties hereto have caused this First Amendment
to be duly executed and delivered by their respective proper and duly authorized
officers as of the day and year first above written.

                                 BIO-PLEXUS, INC.

                                 By:    /s/  John S. Metz
                                        ---------------------------------------
                                 Name:  John S. Metz
                                 Title: President and Chief Executive Officer

                                 APPALOOSA MANAGEMENT L.P.,
                                        as Collateral Agent

                                 By:    Appaloosa Partners Inc., its General
                                                   Partner

                                 By:    /s/  James E. Bolin
                                        ---------------------------------------
                                 Name:  James E. Bolin
                                 Title: Vice President

                                 APPALOOSA INVESTMENT LIMITED
                                          PARTNERSHIP I

                                 By:    Appaloosa Management L.P., its
                                                 General Partner
                                 By:    Appaloosa Partners Inc., its General
                                                   Partner

                                 By:    /s/  James E. Bolin
                                        ---------------------------------------
                                 Name:  James E. Bolin
                                 Title: Vice President



                                 PALOMINO FUND LTD.

                                 By:    Appaloosa Management L.P.
                                        its Investment Advisor

                                 By:    Appaloosa Partners Inc.
                                        its General Partner

                                 By:    /s/  James E. Bolin
                                        ---------------------------------------
                                 Name:  James E. Bolin
                                 Title: Vice President


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                                 TERSK LLC

                                 By:    Appaloosa Management L.P.
                                        its Investment Advisor

                                 By:    Appaloosa Partners Inc.
                                        its General Partner

                                 By:    /s/  James E. Bolin
                                        ---------------------------------------
                                 Name:  James E. Bolin
                                 Title: Vice President


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