SECURITIES AND EXCHANGE COMMISSION

                            Washington, D.C.  20549

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                                  FORM 8-A/A

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


                              Safety-Kleen Corp.
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            (Exact name of registrant as specified in its charter)


           Wisconsin                                         39-6090019
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(State of incorporation or organization)                    (IRS Employer
                                                            Identification No.)

One Brinckman Way, Elgin, Illinois                          60123-7857
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     (Address of principal executive offices)               (Zip Code)


If this Form relates to the registration of a class of debt securities and is
effective upon filing pursuant to General Instruction A(c)(1), please check the
following box.   [_]

If this Form relates to the registration of a class of debt securities and is to
become effective simultaneously with the effectiveness of a concurrent
registration statement under the Securities Act of 1933 pursuant to General
Instruction A(c)(2), please check the following box.  [_]


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

Common Stock Purchase Rights             New York Stock Exchange


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


 
                                     None
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                               (Title of Class)

 
Item 1.   Description of Securities.
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     On November 20, 1997, Safety-Kleen Corp., a Wisconsin corporation (the
"Company"), entered into an Agreement and Plan of Merger (the "Merger
Agreement") with SK Parent Corp., a Delaware corporation ("Parent"), and SK
Acquisition Corp. a Wisconsin corporation ("Purchaser").  On March 9, 1998,
following the failure of the Merger Agreement to win shareholder approval on
that date, the Board of Directors of the Company terminated the Merger
Agreement.

     On March 11, 1998, the Board of Directors, following an unsuccessful
attempt to negotiate improvements to the unsolicited pending exchange offer of
Laidlaw Environmental Services, Inc. ("Laidlaw Environmental") made pursuant to
the Amended Prospectus dated January 28, 1998 ("Amended Prospectus") of Laidlaw
Environmental, adopted a Third Amendment, dated as of March 11, 1998 (the "Third
Amendment"), to the Rights Agreement, dated as of November 9, 1988 (as amended
by the First Amendment dated August 9, 1990 (the "First Amendment") and the
Second Amendment dated November 20, 1997 ("Second Amendment").  The Third
Amendment provided, among other things, that the commencement or consummation
occurring prior to Midnight, Eastern Standard Time on March 27, 1998, of the
exchange offer contemplated by the Amended Prospectus, on the terms therein or
on terms more favorable to shareholders of the Company (provided that prior to
such consummation, Laidlaw Environmental publicly announces (the "Announcement")
that it will effect the back-end merger contemplated by the Amended Prospectus
with per share consideration at least as favorable as the per share
consideration paid in the exchange offer), will not (i) cause Laidlaw
Environmental, LES Acquisition, Inc. ("LES") or any of their respective
Affiliates or Associates to become an "Acquiring Person" (as defined in the
Rights Agreement), (ii) give rise to a "Distribution Date" (as defined in the
Rights Agreement) or (iii) trigger certain other events specified in the Rights
Agreement.

     On March 16, following further negotiations with Laidlaw Environmental, the
Company entered into an Agreement and Plan of Merger (the "LLE Merger
Agreement"), with Laidlaw Environmental and LES.  In connection with the LLE
Merger Agreement, the Board of Directors of the Company approved a Fourth
Amendment, dated March 15, 1998 ("Fourth Amendment") to the Rights Agreement,
dated as of November 9, 1988 (as amended by the First Amendment, the Second
Amendment, the Third Amendment, and the Fourth Amendment, the "Rights Agreement"
(except where the context otherwise requires)) between the Company and The First
National Bank of Chicago, as Rights Agent.  The Fourth Amendment deletes the
provisions relating to Laidlaw Environmental and LES that had been added by the
Third Amendment, and, instead, provides, among other things, that the execution,
delivery and performance of the LLE Merger Agreement will not cause (i) Laidlaw
Environmental, LES or any of their respective Affiliates or Associates to become
an "Acquiring Person" (as defined in the Rights Agreement), (ii) give rise to a
"Distribution Date" (as defined in the Rights Agreement), or (iii) trigger
certain other events specified in the Rights Agreement.

     The following is a description of the Company's Rights Agreement as
amended.

                                      -1-

 
     On November 9, 1988, the Board of Directors of the Company declared a
dividend of one common share purchase right ("Right") on each outstanding share
of the Company's Common Stock, $.10 par value per share (the "Common Shares"),
payable to shareholders of record on November 21, 1988 (the "Record Date").
Each Right entitles the holder thereof to buy one Common Share at an exercise
price of $73.00, subject to adjustment.  The terms of the Rights are set forth
in the Rights Agreement.

     Until the earlier to occur of (i) 10 days following a public announcement
that a person or group of affiliated or associated persons (excluding Laidlaw
Environmental, LES and their respective affiliates and associates unless any
such person acquires beneficial ownership of 20% or more of the outstanding
Common Shares other than pursuant to the terms of the LLE Merger Agreement (an
"Acquiring Person")) have acquired beneficial ownership of 20% or more of the
outstanding Common Shares or (ii) 10 business days (or such later date as may be
determined by action of the Board of Directors prior to such time as any person
or group becomes an Acquiring Person) following the commencement of, or
announcement of an intention to make, a tender offer or exchange offer the
consummation of which would result in the beneficial ownership by a person or
group of affiliated or associated persons of 20% or more of such outstanding
Common Shares (the earlier of such dates being called the "Distribution Date"),
the Rights will be evidenced by Common Share certificates.  Notwithstanding the
foregoing, a Distribution Date shall not be deemed to have occurred solely as a
result of (i) the approval, execution or delivery of the LLE Merger Agreement,
or (ii) commencement or consummation, of the transactions contemplated by the
LLE Merger Agreement.

     A person shall not be deemed to have become an "Acquiring Person" for any
purposes if, as determined in good faith by the Board of Directors, he
inadvertently becomes an Acquiring Person and promptly thereafter divests
himself of sufficient number of Common Shares to no longer be an "Acquiring
Person".

     The Rights Agreement provides that, until the Distribution Date, the Rights
will be transferred with and only with the Common Shares.  Until the
Distribution Date (or earlier redemption or expiration of the Rights), new
Common Share certificates issued after the Record Date will contain a notation
incorporating the Rights Agreement by reference.  Until the Distribution Date
(or earlier redemption or expiration of the Rights), the surrender for transfer
of any certificates for Common Shares will also constitute the transfer of the
Rights associated with the Common Shares represented by such certificate.  As
soon as practicable following the Distribution Date, separate certificates
evidencing the Rights ("Right Certificates") will be mailed to holders of record
of the Common Shares as of the close of business on the Distribution Date and
such separate Right Certificates alone will evidence the Rights.

     The Rights are not exercisable until the Distribution Date.  The Rights
will expire on November 21, 1998 (the "Final  Expiration Date"), unless the
Rights are earlier redeemed by the Company, as described below.

                                      -2-

 
     The Purchase Price payable, and the number of Common Shares or other
securities or property issuable, upon exercise of the Rights are subject to
adjustment from time to time to prevent dilution (i) in the event of a stock
dividend on, or a subdivision, combination or reclassification of, the Common
Shares, (ii) upon the grant to holders of the Common Shares of certain rights or
warrants to subscribe for or purchase Common Shares at a price, or securities
convertible into Common Shares with a conversion price, less than the then
current market price of the Common Shares or (iii) upon the distribution to
holders of the Common Shares of evidences of indebtedness or assets (excluding
regular periodic cash dividends paid out of earnings or retained earnings or
dividends payable in Common Shares) or of subscription rights or warrants (other
than those referred to above).  With certain exceptions, no adjustment in the
Purchase Price will be required until cumulative adjustments require an
adjustment of at least 1% in such Purchase Price.  No fractional Common Shares
will be issued and in lieu thereof, an adjustment in cash will be made based on
the market price of the Common Shares on the last trading day prior to the date
of exercise.

     If any person becomes an Acquiring Person, each holder of a Right, other
than Rights beneficially owned by the Acquiring Person (which will be void),
will have the right to receive upon exercise of such Right that number of Common
Shares having a market value of two times the exercise price of the Right.

     In addition, if the Company is acquired in a merger or other business
combination transaction or 50% or more of its consolidated assets or earning
power are sold, proper provision will be made so that each holder of a Right
will thereafter have the right to receive, upon the exercise thereof at the then
current exercise price of the Right, that number of shares of common stock of
the acquiring company which at the time of such transaction will have a market
value of two times the exercise price of the Right.

     Notwithstanding anything in the Rights Agreement to the contrary, holders
of Rights will not have the right to exercise such Rights as set forth in the
immediately preceding two paragraphs, and the Board of Directors of the Company
will not have the right described in the next paragraph, solely as a result of
(i) the approval, execution or delivery of the LLE Merger Agreement, or (ii) the
commencement or consummation of the transactions contemplated by the LLE Merger
Agreement.

     At any time after a person or group becomes an Acquiring Person and prior
to the acquisition by such person or group of 50% or more of the  outstanding
Common Shares, the Board of Directors of the Company may exchange the Rights
(other than Rights owned by such person or group which have become void), in
whole or in part, at an exchange ratio of one Common Share per Right (subject to
adjustment).

     At any time before a person or group becomes an Acquiring Person, the Board
of Directors of the Company may redeem the Rights in whole, but not in part, at
a price of $.01 per Right, subject to adjustment (the "Redemption Price").  The
redemption of the Rights may be made effective at such time, on such basis and
with such conditions as the Board of Directors

                                      -3-

 
in its sole discretion may establish.  Immediately upon any redemption of the
Rights, the right to exercise the Rights will terminate and the only right of
the holders of the Rights will be to receive the Redemption Price.

     The terms of the Rights may be amended by the Board of Directors of the
Company without the consent of the holders of the Rights, including an amendment
to lower the threshold for exercisability of the Rights from 20% to not less
than the greater of (i) any percentage greater than the largest percentage of
the outstanding Common Shares then known to the Company to be beneficially owned
by any person or group of affiliated or associated persons and (ii) 10%, except
that from and after such time as any person becomes an Acquiring Person no such
amendment may adversely affect the interests of the holders of the Rights.

     Until a Right is exercised, the holder thereof, as such, will have no
rights as a shareholder of the Company, including, without limitation, the right
to vote or to receive dividends.

     The Rights Agreement, dated as of November 9, 1988, between Safety-Kleen
Corp. and The First National Bank of Chicago, as Rights Agent, is filed as
Exhibit 1 to the Company's Registration Statement on Form 8-A dated December 28,
1988.  The First Amendment is filed as Exhibit 1 to the Company's Form 8 dated
August 27, 1990.  The Second Amendment is filed as Exhibit 1.3 to the Company's
Form 8-A/A dated November 20, 1998.  The Third Amendment is filed as Exhibit 1.4
to this Form 8A/A.  The Fourth Amendment is filed as Exhibit 1.5 to this Form
8A/A.  The Board of Directors of the Company adopted a resolution on November
14, 1997 which is described in the Company's Form 8-K dated November 14, 1997.
The foregoing summary description of the Rights does not purport to be complete
and is qualified in its entirety by the reference to such exhibits and Form 8-K,
which are hereby incorporated herein by reference in their entirety.

Item 2.   Exhibits.
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     1.1  Rights Agreement, dated as of November 9, 1988, between Safety-Kleen
          Corp. and The First National Bank of Chicago, as Rights Agent
          (incorporated by reference to the Company's Registration Statement on
          Form 8-A dated December 28, 1988).

     1.2  First Amendment, dated as of August 10, 1990, between Safety-Kleen
          Corp. and The First National Bank of Chicago (incorporated by
          reference to the Company's Form 8 dated August 27, 1990 amending the
          Form 8-A dated December 28, 1988).

     1.3  Second Amendment dated as of November 20, 1997 between Safety-Kleen
          Corp. and The First National Bank of Chicago, as Rights Agent.

                                      -4-

 
     1.4  Third Amendment dated as of March 11, 1997 between Safety-Kleen Corp.
          and the First National Bank of Chicago, as Rights Agent (filed
          herewith).

     1.5  Fourth Amendment, dated as of March 15, 1998, between Safety-Kleen
          Corp. and The First National Bank of Chicago, as Rights Agent (filed
          herewith).

                                      -5-

 
                                  SIGNATURES


     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.



                                      SAFETY-KLEEN CORP.


                                      /s/ DONALD W. BRINCKMAN
                                      ----------------------------------
                                      Donald W. Brinckman
Dated: March 30, 1998                 Chairman and Chief Executive Officer

                                      -6-

 
                               INDEX TO EXHIBITS
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Exhibit
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1.1  Rights Agreement, dated as of November 9, 1988, between Safety-Kleen Corp.
     and The First National Bank of Chicago, as Rights Agent (incorporated by
     reference to the Company's Registration Statement on Form 8-A dated
     December 28, 1988).

1.2  First Amendment, dated as of August 10, 1990, between Safety-Kleen Corp.
     and The First National Bank of Chicago (incorporated by reference to the
     Company's Form 8 dated August 27, 1990 amending the Form 8-A dated December
     28, 1988).

1.3  Second Amendment dated as of November 20, 1997 between Safety-Kleen Corp.
     and The First National Bank of Chicago, as Rights Agent.

1.4  Third Amendment dated as of March 11, 1997 between Safety-Kleen Corp. and
     the First National Bank of Chicago, as Rights Agent (filed herewith).

1.5  Fourth Amendment, dated as of March 15, 1998, between Safety-Kleen Corp.
     and The First National Bank of Chicago, as Rights Agent (filed herewith).