Three successive cross-sectional surveys were used to measure the impact of a restrictive smoking policy on employee smoking patterns, perceived exposure to environmental tobacco smoke, attitudes about the policy, and smoking-related norms in a large decentralized state agency. No significant change was detected in smoking prevalence, the proportion of smokers attempting to quit, or the total daily consumption of cigarettes by smokers. The daily consumption of cigarettes at work decreased significantly, from 16.9% to 4.9% smoking 15 or more cigarettes per day. The proportion of respondents bothered every day by coworkers' smoke dropped from 21.8% to 3.8%. Following policy implementation, the interaction between smokers and nonsmokers about smoking decreased. The findings suggest that restrictive work site smoking policies are effective at decreasing exposure to environmental tobacco smoke, but not, at least in the short run, at lowering smoking prevalence. Also, the decreased interaction regarding smoking may have the unintended consequence of reducing the perceived pressure on smokers to quit.