X0303 4 2010-04-30 0001257640 KRONOS WORLDWIDE INC KRO 0001037854 SIMMONS HAROLD C 5430 LBJ FREEWAY, SUITE 1700 DALLAS TX 75240 1 1 1 0 Chairman of the Board Common Stock $0.01 par value 2010-04-30 4 P 0 100 16.99 A 235609 D Common Stock $0.01 par value 2010-04-30 4 P 0 8 16.87 A 235617 D Common Stock $0.01 par value 2010-04-30 4 P 0 892 16.97 A 236509 D Common Stock $0.01 par value 28995021 I by Valhi Common Stock $0.01 par value 17609635 I by NL Common Stock $0.01 par value 79567 I by TFMC Common Stock $0.01 par value 54856 I by Spouse Common Stock $0.01 par value 2686 I by Contran Directly held by Valhi, Inc. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship to the reporting person. Directly held by NL Industries, Inc. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship to the reporting person. Directly held by TIMET Finance Management Company. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship to the reporting person. Directly held by the reporting person's spouse. The reporting person disclaims beneficial ownership of, and a pecuniary interest in, any shares of the issuer's common stock that his spouse holds. Directly held by Contran Corporation. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship to the reporting person. Exhibit Index Exhibit 99 Additional Information A. Andrew R. Louis, Attorney-in-fact, for Harold C. Simmons 2010-05-04