EXHIBIT 21 EXHIBIT 21 LIST OF SUBSIDIARY CORPORATIONS ARKANSAS BEST CORPORATION The Registrant owns and controls the following subsidiary corporations: Jurisdiction of % of Voting Name Incorporation Securities Owned Subsidiary of Arkansas Best Corporation: ABF Freight System, Inc. Delaware 100 Treadco, Inc. Delaware 45.7 Transport Realty, Inc. Arkansas 100 Data-Tronics Corp. Arkansas 100 Clover Insurance Company, Ltd. Bermuda 100 Arkansas Underwriters Corporation Arkansas 100 Advertising Counselors, Inc. Arkansas 100 ABF Cartage, Inc. Delaware 100 ABF Farms, Inc. Arkansas 100 Land-Marine Cargo, Inc. Puerto Rico 100 Integrated Distribution, Inc. Arkansas 100 ABF Freight System Canada, Ltd. Canada 100 ABF Freight System de Mexico, Inc. Delaware 100 Best Logistics, Inc. Delaware 100 Agile Freight System, Inc. Delaware 100 Agricultural Express of America, Inc. Delaware 100 Clipper Exxpress Company Delaware 100 WorldWay Corporation North Carolina 100 Subsidiary of ABF Freight System, Inc.: ABF Freight System (B.C.), Ltd. British Columbia 100 Subsidiary of Treadco, Inc.: Trans World Casings, Inc. Delaware 100 Subsidiary of WorldWay Corporation G.I. Trucking Company California 100 Cardinal Freight Carriers, Inc. Virginia 100 CaroTrans International, Inc. North Carolina 100 The Complete Logistics Company California 100 Innovative Logistics Incorporated South Carolina 100 Motor Carrier Insurance, Ltd. Bermuda 100 Carrier Computer Services, Inc. North Carolina 100 Carolina Breakdown Service, Inc. North Carolina 100 Hawaiian Pacific Freight Forwarding California 100