<PAGE>
 


                                   FORM 8-A

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549


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


                 Primus Telecommunications Group, Incorporated
               -------------------------------------------------
            (Exact name of registrant as specified in its charter)


         Delaware                                         54-1708481
- - --------------------------                        --------------------------
(State of incorporation or                           (I.R.S. Employer
 organization                                         Identification No.)




              8180 Greensboro Drive, Suite 1100, McLean, VA 22102
              ---------------------------------------------------
              (Address of principal executive offices) (zip code)



       Securities to be registered pursuant to Section 12(b) of the Act:
                                     None.


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

                         Common Stock, $.01 par value
                         ----------------------------
                               (Title of class)

<PAGE>
 
Item 1.   Description of Registrant's Securities To Be Registered.
          --------------------------------------------------------

          Registrant's Common Stock, par value $.01 per share, is described
under the caption "Description of Capital Stock - Common Stock" at page 67 of
the Registrant's Registration Statement on Form S-1 ("Registration Statement"),
which was filed with the Securities and Exchange Commission under the Securities
Act of 1933 on August 27, 1996 and subsequently amended on October 11, 1996 and
October 25, 1996.  A copy of page 67 of the Registration Statement is filed
herewith and the description of the Common Stock is incorporated herein by
reference.

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

          Exhibit    Description 
          -------    -----------
          1          Form of Common Stock Certificate of the Registrant. (To be 
                     filed by amendment).

          2          Registrant's Certificate of Incorporation, as amended.
                     (Incorporated by reference to Exhibit 3.1 of the
                     Registration Statement).

          3          Form of Registrant's Amended and Restated Bylaws.
                     (Incorporated by reference to Exhibit 3.2 of the
                     Registration Statement).

          4          Page 67 of the Prospectus included in the Registration
                     Statement, containing the section entitled "Description of
                     Capital Stock - Common Stock."

<PAGE>
 
                                   SIGNATURE
                                   ---------

          Pursuant to the requirements of Section 12 of the Securities Exchange 
Act of 1934, Registrant has duly caused this Registration Statement to be signed
on its behalf by the undersigned, thereto duly authorized.

                                                 PRIMUS TELECOMMUNICATIONS
                                                 GROUP, INCORPORATED

Date: October 29, 1996                           By: /s/ Thomas R. Kloster
                                                     --------------------------
                                                     Thomas R. Kloster
                                                     Corporate Controller

<PAGE>
 
                                 EXHIBIT INDEX


Exhibit
  No.         Description
- - -------       -----------

  4           Page 67 of the Prospectus
              included in the Registration
              Statement, containing the section
              entitled "Description of Capital
              Stock - Common Stock."





<PAGE>
 
                         DESCRIPTION OF CAPITAL STOCK
 
COMMON STOCK
 
  The Company is authorized to issue up to 40,000,000 shares of Common Stock,
par value $0.01 per share. As of October 25, 1996, the Company had 10,490,391
shares outstanding, 1,635,559 shares of Common Stock reserved for issuance upon
exercise of options granted pursuant to the Plans. An additional 1,294,566
shares of Common Stock may be issued pursuant to the Soros/Chatterjee Warrants
assuming such warrants were exercised on the date of the Offering at an assumed
offering price of $15. The actual number of shares of Common Stock issuable
under the Soros/Chatterjee Warrants will be up to 627,899 shares plus an
indeterminate number of shares having a fair market value of $10 million as of
the date of exercise. Holders of shares of Common Stock are entitled to one vote
per share on all matters to be voted upon by the stockholders. Subject to such
preferential rights of the issued and outstanding Series A Stock more
particularly described below, and such preferential rights as the Company's
Board of Directors may grant in connection with future issuances of Preferred
Stock, holders of shares of Common Stock are entitled to receive such dividends
as the Board of Directors
 may declare in its discretion out of funds legally
available therefor. In the event of a liquidation, dissolution or winding up of
the Company, after payment of liabilities and any liquidation preference on any
shares of Preferred Stock then outstanding, the holders of shares of Common
Stock are entitled to a distribution of any remaining assets of the Company.
Holders of shares of Common Stock have no cumulative voting or preemptive
rights. All outstanding shares of Common Stock are, and the shares of Common
Stock offered hereby, when issued and paid for, will be, fully paid and
nonassessable.
 
PREFERRED STOCK
 
  The Company is authorized to issue up to 2,455,000 shares of Preferred Stock,
par value $0.01 per share, of which 455,000 shares are designated Series A
Stock. All shares of the Series A Stock were issued to the sellers in the
Axicorp transaction, 206,666 shares of which were delivered at closing and the
balance of which are being held by the Company to secure certain post-closing
obligations of the sellers. As a consequence of the consummation of the
Offering, all of the Series A Stock will convert into Common Stock on a 3.381 to
one basis.
 
  Dividends are paid on Series A Stock when, as and in the same amount as paid
from time to time on the Common Stock. Holders of Series A Stock are not
entitled to vote on matters related to the Company other than certain matters
related to the capital structure of the Company or matters for which the law
provides for such vote. If the Company grants preemptive rights in connection
with certain issuances, sales or exchanges of Common Stock of the Company or
of securities convertible into Common Stock of the Company, holders of Series
A Stock are also granted such preemptive rights. A holder of Series A Stock
has the right at any time after March 1, 1998 to convert its Series A Stock,
share for share, into Common Stock of the Company. Upon the occurrence of
certain events, including the elimination of certain foreign ownership
restrictions on the Company, the occurrence of certain transfers of the
Company's stock or assets, or the public offering of more than 20% of the
Company's Common Stock, shares of Series A Stock automatically convert into
shares of Common Stock of the Company. Any particular conversion of shares of
Series A Stock held by certain foreign owners into shares of Common Stock of
the Company may be limited by foreign ownership restrictions applicable to the
Company.
 
  In addition to the Series A Stock, the Company, without further action by
the Stockholders, is also authorized to issue up to 2,000,000 shares of other
Preferred Stock, par value $0.01 per share ("Other Preferred Stock"). The
Company's Board of Directors may determine the timing, series, designation and
number of shares of Other Preferred Stock to be issued, as well as the rights,
preferences and limitations of such shares, including those related to voting
power, redemption, conversion, dividend rights and liquidation preferences.
The issuance of Other Preferred Stock could adversely affect the voting power
of the holders of Common Stock of the Company or have the effect of deterring
or delaying any attempt by a person, entity or group to obtain control of the
Company. See "--Takeover Protection."
 
                                      67