PROMISSORY NOTE

$31,422,500                     September 24, 2004                 Dallas, Texas

         FOR VALUE RECEIVED, the undersigned, Kronos Worldwide, Inc., a Delaware
corporation,  unconditionally  promises  to pay to the  order of NL  Industries,
Inc., a New Jersey corporation, in lawful money of the United States of America,
the  principal  sum of THIRTY ONE MILLION FOUR HUNDRED  TWENTY TWO THOUSAND FIVE
HUNDRED and NO/100ths DOLLARS ($31,422,500) together with interest from the date
of this Note on the unpaid  principal  balance from time to time pursuant to the
terms of this Note.  This Note shall be unsecured  and will bear interest on the
terms set forth in  Section 5 below.  Capitalized  terms not  otherwise  defined
shall have the meanings given to such terms in Section 15 of this Note.

         Section 1.  Replacement of Prior  Promissory Note. This Note along with
the Other Promissory  Notes together  divide,  amend and replace in its entirety
the Promissory Note dated December 8, 2003 in the original  principal  amount of
$200 million  executed by Maker and payable to the order of Payee (the "Original
Note"). All accrued and unpaid interest outstanding on the Original Note through
September 23, 2004 has been paid by Maker to Payee.

         Section  2.  Place of  Payment.  All  payments  will be made at Payee's
address at Three Lincoln Centre,  5430 LBJ Freeway,  Suite 1700,  Dallas,  Texas
75240-2697,  or such other place as the Payee may from time to time designate in
writing, in immediately available funds, without setoff or counterclaim.

         Section 3. Payment.  The principal  balance of this Note and any unpaid
and accrued  interest  thereon  shall be due and payable on the Maturity Date or
upon   acceleration  as  provided   herein.   Prior  to  the  Maturity  Date  or
acceleration,  unpaid and accrued interest on the outstanding  principal balance
of this Note shall be due and payable  quarterly on March 31, June 30, September
30 and December 31 of each year; provided,  however, that such day is a business
day, and if such day is not a business day, the quarterly interest payment shall
be due the next successive business day.

         Section 4.  Prepayment.  This Note may be prepaid in part or in full at
any time without penalty; provided, however,  prepayments shall be first applied
to accrued and unpaid interest and then to principal.

         Section 5. Interest.  The unpaid balance of this Note (exclusive of any
past due principal)  shall bear interest at an annual rate of nine percent (9%).
Ten business  days after the Maturity Date or  acceleration  as provided in this
Note,  all past due  principal  and past due interest  owed under this Note will
bear interest at an annual rate of twelve percent (12%). Accrued interest on the
unpaid principal of this Note shall be computed on the basis of a 365 or 366-day
year, as the case may be, for actual days elapsed. In no event,  however,  shall
such  computation  result in an amount of accrued  interest  that  would  exceed
accrued interest on the unpaid  principal  balance during the same period at the
Maximum Rate.  Notwithstanding  anything to the contrary, this Note is expressly
limited so that in no contingency or event  whatsoever  shall the amount paid or
agreed  to be  paid  to  the  Payee  exceed  the  Maximum  Rate.  If,  from  any
circumstances  whatsoever,  the Payee  shall ever  receive as interest an amount
that would exceed the Maximum Rate, such amount received that would be in excess
of the Maximum Rate shall be applied to the  reduction  of the unpaid  principal
balance and not to the payment of interest,  and if the principal amount of this
Note is paid in full, any remaining  excess shall be paid to Maker,  and in such
event, the Payee shall not be subject to any penalties  provided by any laws for
contracting for, charging,  taking, reserving or receiving interest in excess of
the highest lawful rate permissible under applicable law.

         Section 6. Remedy.  Upon the occurrence and during the  continuation of
an Event of  Default,  Payee may,  at its  option,  declare  the  entire  unpaid
principal  of this Note,  and all accrued  interest  and other  amounts  payable
hereunder,  immediately due and payable without presentment,  demand, protest or
other notice of any kind, all of which are expressly  waived by Maker,  and upon
such  declaration,  such amounts shall become and shall be  immediately  due and
payable.  The Payee  shall have all of the rights and  remedies  provided in the
applicable  Uniform  Commercial  Code or in this  Note  or any  other  agreement
between  Maker and in favor of the Payee,  as well as those  rights and remedies
provided  by any other  applicable  law,  rule or  regulation.  All  rights  and
remedies  of  the  Payee  are  cumulative   and  may  be  exercised   singly  or
concurrently.  The  exercise  of any right or remedy will not be a waiver of any
other  right or  remedy.  Failure  to  exercise  any  right or  remedy  upon the
occurrence of an Event of Default shall not  constitute a waiver of the right to
exercise  such right or remedy  upon the  occurrence  of a  subsequent  Event of
Default.

         Section 7. Right of  Offset.  The Payee  shall have the right of offset
against  amounts  that may be due by the  Payee  now or in the  future  to Maker
against amounts due under this Note.

         Section 8. Record of Outstanding Principal. The date and amount of each
repayment of principal outstanding under this Note shall be recorded by Payee in
its records.  The aggregate unpaid principal  balance so recorded by Payee shall
be the best evidence of the principal  balance owing and unpaid under this Note;
provided that the failure of Payee to so record any such balance or any error in
so  recording  any  such  balance  shall  not  limit  or  otherwise  affect  the
obligations of Maker under this Note to repay the principal balance  outstanding
and all accrued or accruing interest.

         Section 9. Waiver.  Maker and each  surety,  endorser,  guarantor,  and
other party now or subsequently liable for payment of this Note, severally waive
demand, presentment for payment, notice of dishonor, protest, notice of protest,
diligence in  collecting or bringing suit against any party liable on this Note,
and further agree to any and all extensions,  renewals,  modifications,  partial
payments,  substitutions of evidence of indebtedness,  and the taking or release
of any collateral with or without notice before or after demand by the Payee for
payment under this Note.

         Section 10. Costs and  Attorneys'  Fees.  In the event the Payee incurs
costs in  collecting  on this  Note,  this  Note is  placed  in the hands of any
attorney for collection, suit is filed on this Note or if proceedings are had in
bankruptcy, receivership, reorganization, or other legal or judicial proceedings
for the collection,  Maker and any guarantor  jointly and severally agree to pay
on demand to the Payee all expenses and costs of collection,  including, but not
limited to,  attorneys'  fees incurred in connection  with any such  collection,
suit, or proceeding, in addition to the principal and interest then due.

         Section 11. Time of Essence. Time is of the essence with respect to all
of Maker's obligations and agreements under this Note.

         Section 12.  Jurisdiction and Venue. This Note shall be governed by and
construed in accordance  with the domestic  laws of the state of Texas,  without
giving effect to any choice of law or conflict of law provision or rule (whether
of  the  state  of  Texas  or any  other  jurisdiction)  that  would  cause  the
application of the laws of any jurisdiction other than the state of Texas. Maker
consents to jurisdiction in the courts located in Dallas, Texas.

         Section 13. Notice. Any notice or demand required by this Note shall be
deemed to have been given and  received on the earlier of (i) when the notice or
demand is actually  received by the  recipient or (ii) 72 hours after the notice
is deposited in the United States mail,  certified or  registered,  with postage
prepaid, and addressed to the recipient. The address for giving notice or demand
under  this Note (i) to the Payee  shall be the place of  payment  specified  in
Section 1 or such other  place as the Payee may  specify in writing to the Maker
and (ii) to the Maker shall be the address  below the Maker's  signature or such
other place as the Maker may specify in writing to the Payee.

         Section 14. Successors and Assigns. All of the covenants,  obligations,
promises  and  agreements  contained in this Note made by Maker shall be binding
upon its successors and assigns;  notwithstanding the foregoing, Maker shall not
assign this Note or its  performance  under this Note without the prior  written
consent of the Payee.

         Section 15. Definitions. For purposes of this Note, the following terms
shall have the following meanings:

                  (a) "Event of Default" shall mean the failure by Maker to make
         when due a punctual  payment of principal of, or interest on, this Note
         within thirty (30) days  following the date such amount becomes due and
         payable in accordance with the terms of this Note.

                  (b) "Maker"  shall mean  Kronos  Worldwide,  Inc.,  a Delaware
         corporation.

                  (c) "Maturity Date" shall mean December 31, 2010.

                  (d)  "Maximum   Rate"  shall  mean  the  highest  lawful  rate
         permissible under applicable law for the use,  forbearance or detention
         of money.

                  (e) "Other  Promissory  Notes"  shall mean (i) the  Promissory
         Note  of  even  date  herewith  in the  original  principal  amount  of
         $6,077,500 payable to order of Valhi, Inc., a Delaware corporation, and
         executed by Maker and (ii) the Promissory Note of even date herewith in
         the  original  principal  amount of  $162,500,000  payable  to order of
         Valcor, Inc., a Delaware corporation, and executed by Maker.

                  (f) "Note" shall mean this Promissory Note.

                  (g)  "Payee"  shall  mean NL  Industries,  Inc.,  a New Jersey
         corporation, or subsequent holder of this Note.

         EXECUTED as of September 24, 2004.

                                       MAKER:

                                       KRONOS WORLDWIDE, INC.




                                       By: /s/ Gregory M. Swalwell
                                           -------------------------------------
                                           Gregory M. Swalwell, Vice President

                                       Address:     Three Lincoln Centre
                                                    5430 LBJ Freeway, Suite 1700
                                                    Dallas, Texas   75240-2697