SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                                   __________

                                    FORM 8-A

                FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                     PURSUANT TO SECTION 12(b) OR (g) OF THE
                         SECURITIES EXCHANGE ACT OF 1934


                              CENTRA SOFTWARE, INC.
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             (Exact name of registrant as specified in its charter)


       Delaware                                                 04-3268918
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(State of incorporation or organization)                    (IRS Employer
                                                            Identification No.)


430 Bedford Street, Lexington, MA                                02420
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(Address of principal executive offices)                       (Zip Code)


                                                        
       If this form relates to the registration of a       If this form relates to the registration of a
       class of securities pursuant to                     class of securities pursuant to
       Section 12(b) of the Exchange Act and is            Section 12(g) of the Exchange Act and is
       effective pursuant to General                       effective pursuant to General
       Instruction A.(c), check the following box:         Instruction A.(d), check the following box.
       [_]                                                 [X]




Securities Act registration statement file number to which this form relates (if
applicable): Not applicable.

Securities to be registered pursuant to Section 12(b) of the Act:

       Title of each class                    Name of each exchange on which
       to be so registered                    each class is to be registered
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                                  None.

Securities to be registered pursuant to Section 12(g) of the Act:

                           Rights to Purchase Series A
                    Participating Cumulative Preferred Stock
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                                (Title of Class)



Item 1. Description of Securities to be Registered.
        ------------------------------------------

        On April 19, 2002, we adopted a stockholder rights plan. The rights plan
is designed to help ensure that all of our stockholders receive fair and equal
treatment in the event of any unsolicited proposal to acquire control of our
company. As part of the rights plan, we designated 300,000 shares of our
authorized preferred stock as series A preferred stock. The adoption of our
stockholder rights plan will affect the rights of holders of our common stock,
and any issuance of shares of series A preferred stock upon exercise of the
rights will also affect the rights of holders of common stock.

        We have incorporated by reference as exhibits to this registration
statement copies of the rights agreement specifying the terms of the rights, the
certificate of designation specifying the terms of our series A preferred stock
and the form of right certificate. The following is a summary of the material
terms of our rights plan and the underlying series A preferred stock. This
summary is qualified in its entirety by reference to the exhibits incorporated
by reference in this registration statement.

Our stockholder rights plan

        On April 19, 2002, our board of directors declared a distribution of one
right for each outstanding share of our common stock. We will issue these rights
to our stockholders of record on May 15, 2002. After that date, unless the
rights have been redeemed or have expired, we will issue rights with respect to
shares of common stock issued before the rights become exercisable as described
below and, in certain circumstances, with respect to shares of common stock
issued after the rights become exercisable. Each right, when it becomes
exercisable will initially entitle the holder to purchase from us one
one-thousandth (1/1,000) of a share of series A preferred stock for $29. The
description and terms of the rights are set forth in a rights agreement between
us and American Stock Transfer & Trust Company, which is acting as the rights
agent.

        Initially the rights are not exercisable and the certificates
representing shares of common stock evidence the rights. Accordingly, the rights
are initially transferable only with the common stock. The rights become
exercisable upon the earliest of the following dates:

     .  the date on which we first publicly announce that a person or group
        has become an "acquiring person"

     .  the date, if any, that our board of directors may designate following
        the commencement of, or first public disclosure of an intent to
        commence, a tender or exchange offer which could result in the potential
        buyer becoming the beneficial owner of 15% or more of our outstanding
        common stock, including common stock that we will issue upon the
        exchange or redemption of exchangeable shares

        Subject to certain exceptions, an "acquiring person" is any person or
group that, together with its affiliates and associates, has acquired, or has
obtained the right to acquire, beneficial ownership of 15% or more of our
outstanding common stock, including common stock that we will issue upon the
exchange or redemption of exchangeable shares. As soon as practicable following
the date that the rights become exercisable, we will mail separate certificates

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evidencing the rights to stockholders of record as of the close of business on
that date. Thereafter, the separate right certificates will evidence the rights.
The rights will expire on April 19, 2012, unless we redeem them on an earlier
date.

     If our common stock or series A preferred stock changes in any way, then
our board of directors may adjust any of the following in order to preserve the
actual or potential economic value of the rights:

  .  the number of shares of series A preferred stock or other securities
     issuable upon exercise of a right

  .  the exercise price of series A preferred stock

  .  the redemption price of series A preferred stock

  .  the number of rights associated with each share of common stock

     We may issue shares of series A preferred stock in fractions which are an
integral multiple of one one-thousandth (1/1,000) of a share of series A
preferred stock. Though not required to do so, we may issue fractions of shares
upon the exercise of rights. In lieu of fractional shares, we may issue
certificates or utilize a depository arrangement as provided by the terms of the
series A preferred stock. In the case of fractions other than one one-thousandth
(1/1,000) of a share of series A preferred stock or integral multiples thereof,
we may make a cash payment based on the market price of these shares.

     When there is an acquiring person, the rights will entitle each holder to
purchase, for $29, that number of one one-thousandths (1/1,000) of a share of
our series A preferred stock equivalent to the number of shares of our common
stock which at the time of the transaction would have a market value of $58.
However, the rights held by an acquiring person will be null and void and
nontransferable, and any holder, purported transferee or subsequent holder of
these rights will lack any right to exercise or transfer these rights.

     The rights plan contains provisions that are intended to substantially
preserve the value of the rights after they become exercisable if we merge or
consolidate with an acquiring person or its affiliates or associates. Likewise,
the rights plan contains provisions that are intended to substantially preserve
the value of the rights after they become exercisable if we sell, lease,
exchange or transfer 50% or more of our assets, or assets representing 50% or
more of our earning power, to an acquiring person or its affiliates or
associates.

     At any time after there is an acquiring person, our board of directors may
exchange all or part of the then-outstanding rights, other than those rights
that are null and void and nontransferable as described above. The consideration
per right for this exchange will consist of one-half of the securities that
otherwise would have been issuable to the holder of each right upon exercise of
the right. In substitution for shares of series A preferred stock, we may also
issue shares of common stock having an equivalent market value to the shares of
series A preferred stock if at that time either of the following conditions
applies:

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  .  we have a sufficient number of shares of common stock issued but not
     outstanding

  .  we have a sufficient number of shares of common stock authorized but
     unissued

     Our board may redeem all, but not less than all, of the rights at a price
of $.001 per right at any time prior to the earlier of the following dates:

  .  the date on which the rights expire

  .  the date on which we first publicly announce that there is an acquiring
     person

     Our board may pay the redemption price either in cash, in shares of our
common stock, or in any of our securities that our board deems to be at least
equivalent in value.

     If our board elects to redeem the rights, then we will announce the
redemption. Once we announce the redemption, the right to exercise the rights
will terminate and the holders of the rights will be entitled to receive the
redemption price. Until a right is exercised, holders will have no additional
rights as stockholders. Such additional rights include, without limitation,
additional rights to vote or to receive dividends.

     We may supplement or amend the rights agreement in any way and at any time
before the rights become exercisable, except that we may not do so in order to
reduce the redemption price or provide for an earlier expiration of the rights.
Our authority to supplement or amend the rights agreement includes the
provisions concerning the date on which the rights become exercisable, the time
during which we may redeem the rights, and the terms of the series A preferred
stock. We may supplement or amend the rights agreement without the approval of
any holder of the rights.

     The rights have certain anti-takeover effects. The rights will cause
substantial dilution to a person or group that attempts to acquire us without
conditioning the offer on substantially all the rights being acquired. However,
the rights will not interfere with any merger or other business combination with
a third party for which our board of directors grants its approval. This is so
because our board may amend the rights plan or redeem the then-outstanding
rights before that third party has become an acquiring person.

Our series A preferred stock

     We are authorized to issue shares of series A preferred stock, $.001 par
value. The series A preferred stock is entitled to all the rights and privileges
set forth in our articles of organization and contains the features described
below.

     If we declare dividends on shares of our common stock, then at the same
time we will also pay cash and in-kind dividends to record holders of our series
A preferred stock. The payment per shares of series A preferred stock will be
equal to 1,000 times the per share amount of all cash dividends that we are then
paying on each share of common stock. This amount is subject to adjustment to
reflect stock dividends, subdivisions or combinations of our outstanding common
stock. The holders of series A preferred stock are also entitled to receive
quarterly

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cumulative dividends payable in cash in an amount equal to $10.00 per whole
share. However, we will reduce these payments of quarterly cumulative dividends
by whatever amount that we have paid the holders of series A preferred stock in
cash and in-kind dividends as described above. Holders of our series A preferred
stock may vote on each matter on which holders of our common stock may vote.
Series A preferred stock holders will have 1,000 votes for each whole share of
series A preferred stock that they hold. This amount is also subject to
adjustment as described above. Holders of any fraction of a share of series A
preferred stock that is not smaller than one one-thousandth (1/1,000) of a share
will be entitled to vote such fraction. If the equivalent of six quarterly
dividends are in default, then series A preferred stock holders will have
certain special voting rights in the election of directors.

         Whenever quarterly dividends or distributions on outstanding shares of
our series A preferred stock are in arrears, our right to benefit holders of
shares of stock ranking junior to or on a parity with the series A preferred
stock will be subject to certain restrictions. These benefits may include our
declaration or payment of dividends or other distributions on the stock, and our
redemption or purchase of the shares of the stock.

         If we voluntarily or involuntarily liquidate, dissolve or wind up our
affairs, then the series A preferred stock holders will receive an amount equal
to the accrued dividends thereon plus the greater of the following amounts:

     .   $10.00 per whole share

     .   an amount per share equal to 1,000 times the amount per share that we
         distribute to holders of common stock, subject to adjustment as
         described above

         We will distribute this amount to the holders of series A preferred
stock before we make any distribution to the holders of stock ranking on a
parity with the series A preferred stock, other than a ratable distribution, and
also before we make any distribution to holders of stock ranking junior to the
series A preferred stock.

         The shares of series A preferred stock may not be redeemed. However, we
may purchase shares of series A preferred stock in the open market or pursuant
to an offer to any holder.

         If we engage in a consolidation, merger or other transaction in which
the shares of common stock are exchanged for or converted to other securities,
cash or any other property, the shares of series A preferred stock will be
similarly exchanged or converted.

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         We may issues shares of series A preferred stock in whole shares or in
any fraction of a share that is not smaller than one one-thousandth of a share
or any integral multiple of such fraction, subject to certain adjustments. In
lieu of issuing fractional shares, we may issue certificates of depositary
receipts evidencing such authorized fractions of shares. In the case of
fractions other than one one-thousandth (1/1,000) of a share and integral
multiples thereof, we may pay registered holders cash equal to the same fraction
of the current market value of any outstanding shares of series A preferred
stock or the equivalent number of shares of common stock.

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Item 2.  Exhibits.
         --------

         1.       Rights Agreement, dated as of April 19, 2002, between Centra
                  Software, Inc. and American Stock Transfer & Trust Company as
                  Rights Agent (incorporated by reference to Exhibit 4.1 of our
                  current report on Form 8-K filed with the SEC on April 22,
                  2002).

         2.       Certificate of Designation, Preferences and Rights of Series A
                  Participating Cumulative Preferred Stock of Centra Software,
                  Inc. (incorporated by reference to Exhibit 4.2 of our current
                  report on Form 8-K filed with the SEC on April 22, 2002).

         3.       Form of Right Certificate (incorporated by reference to
                  Exhibit 4.3 of our current report on Form 8-K filed with the
                  SEC on April 22, 2002).

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                                    SIGNATURE

         Pursuant to the requirements of Section 12 of the Securities Exchange
Act of 1934, the registrant has duly caused this registration statement to be
signed on its behalf by the undersigned, thereunto duly authorized.

                                            CENTRA SOFTWARE, INC.


Dated: April 22, 2002                       By:  /s/ LEON NAVICKAS
                                               --------------------------------
                                                  Leon Navickas
                                                  Chief Executive Officer

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