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                                                                    EXHIBIT 99.6
 
                            SECURED PROMISSORY NOTE
 
$
- ------------------                                      ------------------, 1998
 
   
     FOR VALUE RECEIVED, the undersigned                ("Borrower") hereby
promises to pay to the order of Superior National Insurance Group, Inc., a
Delaware corporation ("Payee"), the principal sum of
($          ), together with interest on the unpaid balance of such principal
amount from the date hereof at the rate of interest equal to                [the
rate of interest established by the Board of Directors of the Payee on the
record date of the Rights Offering, as defined in that certain Securities Pledge
Agreement dated as of even date herewith by and between Payee and Borrower (the
"Pledge Agreement")]. Accrued interest to be paid on this Secured Promissory
Note (this "Promissory Note") shall be payable in arrears commencing on December
31, 1998 (with respect to interest accrued from the date hereof) and continuing
on each succeeding December 31 thereafter with respect to interest accrued
during the previous year ending December 31 until this Note is paid in full. The
principal balance of, and all accrued and unpaid interest on, this Promissory
Note shall be payable in full by Borrower on the earlier to occur of (i) that
date which is ten (10) years from the date hereof or (ii) termination of
Borrower's employment or consulting relationship with the Payee, its affiliates,
or Comprehensive Compensation Claims Management, Inc. ("3CM").
    
 
     Payments of principal and interest on this Promissory Note shall be made in
legal tender of the United States of America and shall be made at such place as
Payee shall have designated to Borrower (and may be made by payroll deduction by
mutual consent of Borrower and Payee). If the date set for any payment of
principal or interest on this Promissory Note is a Saturday, Sunday or legal
holiday, then such payment shall be due on the next succeeding business day.
 
     As of the date hereof, Borrower has purchased certain shares of common
stock of the Payee, par value $.01 per share, pursuant to the terms of that
certain Stock Subscription Agreement dated as of even date herewith, by and
between Payee and Borrower (the "Subscription Agreement"). Payment of this
Promissory Note shall be secured by the Securities, as defined in that certain
Securities Pledge Agreement dated as of even date herewith by and between Payee
and Borrower (the "Pledge Agreement").
 
     The principal balance of, and accrued and unpaid interest on, this
Promissory Note may be prepaid at any time, in whole or in part, without premium
or penalty. Any such prepayment shall be first applied to the payment of any
accrued and unpaid interest and then to the unpaid balance of the principal
amount.
 
     If Event of Default, as defined in the Pledge Agreement, shall occur, Payee
may accelerate this Promissory Note and declare the entire unpaid principal
amount of this Promissory Note and all accrued and unpaid interest hereon to be
immediately due and payable and, thereupon, the unpaid principal amount and all
such accrued and unpaid interest shall become and be immediately due and
payable, without notice of default, presentment or demand for payment, protest
or notice of nonpayment or dishonor, or other notices or demands of any kind
(all of which are hereby expressly waived by Borrower). The failure of Payee to
accelerate this Promissory Note shall not constitute a waiver of any of Payee's
rights under this Promissory Note as long as Borrower's default under this
Promissory Note or breach of or default under the Subscription Agreement or the
Pledge Agreement continues.
 
     The provisions of this Promissory Note shall be governed by and construed
in accordance with the laws of the State of California without regard to the
conflicts of law rules thereof. In the event that Payee is required to take any
action to collect or otherwise enforce payment of this Promissory Note, Borrower
agrees to pay such reasonable attorneys' fees, court costs and other expenses as
Payee may incur as a result thereof, whether or not suit is commenced.
 
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     All notices, requests, demands or other communications under this
Promissory Note shall be delivered in accordance with the provisions of Section
8.6 of the Subscription Agreement to the address(es) set forth therein.
 
     IN WITNESS WHEREOF, this Promissory Note has been duly executed and
delivered by Borrower on the date first above written.
 
                                          BORROWER:
 
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