To describe the nature, extent, and public health significance of state legislation that preempts the local regulation of tobacco. A computerized database of local tobacco control ordinances, state tobacco control laws, preemption bills introduced during the 1996 state legislative session, articles obtained through a MEDLINE search (1984-1996) using the key word "preemption" or identified from bibliographies of these articles, public opinion surveys, and newspaper articles. All identified data sources were used. Content analyses of preemption bills and state laws were conducted independently by multiple observers. There has been a striking increase in the adoption of local tobacco control ordinances during the past decade; by the end of 1995, approximately 1006 communities had enacted a local tobacco control ordinance. In response, the tobacco industry has advanced legislation in 29 states that preempts local authority to regulate tobacco. During the 1996 state legislative session alone, 26 bills containing preemption were introduced, and 2 were enacted. Emerging trends in the tobacco industry's strategy to advance preemption laws include (1) amending legitimate tobacco control bills to preempt local tobacco regulation, (2) using the Synar amendment as a vehicle to advance preemption, and (3) promoting "superpreemption" bills that eliminate all local control of tobacco policy. Preemption of local tobacco regulation is an important tobacco industry strategy that undermines the public's health. Preventing the enactment of new preemption laws and repealing existing ones should become a public health priority.