Modern transportation methods have facilitated an extensive trade in used tires at the national and international level. The history and reasons for this trade are described. Comprehensive data on United States imports and United States, Japanese, and Korean exports of used tires for the period 1978-85 reveal an unprecedented potential for the worldwide dispersal of important vector mosquitoes such as Aedes albopictus and Ae. aegypti. Other articles of commerce with similar potential may await recognition.