OBJECTIVE: To prepare a history of the enactment of California Assembly Bill 13 (AB 13), a state law prohibiting smoking in most workplaces passed in 1994, and to discuss its initial impacts. METHODS: Data were gathered from open ended interviews with representatives of voluntary health organisations, local government organisations, and principal legislators involved in the process, as well as observers around the state who could provide insight into the legislative process. Information was also obtained from legislative hearings and debates, public documents, letters and personal communications, internal memoranda, and news reports. RESULTS: The success of local tobacco control legislation in California led to a situation in which some health groups were willing to accept state preemption in order to attract the support of the state restaurant association for a bill. The decision to accept this preemption compromise was made by the state level offices of the voluntary health agencies without consulting the broader tobacco control community within California. In contrast, local tobacco control advocates did not accept this compromise, in part because of their belief that local legislation was a better device to educate the public, generate media coverage, and build community support for enforcement and implementation of clean indoor air and other tobacco control laws. Enactment of AB 13 was associated with a slowing of all local tobacco control legislation, including youth oriented laws. CONCLUSIONS: Because its supporters initially doubted that AB 13 would pass, there was never an effort to reconcile the policy differences between state oriented and locally oriented tobacco control policies. This lack of consensus, combined with the political realities inherent in passing any state legislation, led to a bill with ambiguous preemption language which replaced the "patchwork of local laws" with a "patchwork of local enforcement."