Smoke-free air policies have been shown to reduce smoking, but the mechanism of behavior change is not well understood. The authors used structural equation modeling to conduct a theory of planned behavior analysis with data from 395 smokers living in seven Texas cities, three with a comprehensive smoke-free air law and four without a comprehensive law. Agreement with regulating smoking in public places was significantly associated with attitudes and perceived normative pressure about quitting. Nicotine dependence was significantly associated with attitudes and perceived behavioral control. There was also a direct effect of nicotine dependence on intention to take measures to quit smoking. Smoke-free air laws appear to influence quitting intentions through the formation of positive attitudes about regulating smoking in public places and the perception of normative pressure to take measures to quit. Implications for smoke-free air policy campaigns and challenges in evaluating their effectiveness are discussed. (Contains 1 table and 2 figures.)