摘要:OBJECTIVES. Laws restricting smoking in public places and workplaces can protect the public only if they are obeyed. We sought to assess compliance with a Cambridge, Mass, no-smoking ordinance. METHODS. We prospectively observed 174 retail stores 1 month before and 3, 11, and 24 months after the law took effect. At 24 months, we interviewed one employee per store. RESULTS. Full compliance with the law was low; at 24 months, only 4% of stores displayed the mandated sign and were free of smokers and smoke. Fewer than half the stores posted any no-smoking sign. Sign prevalence increased over 2 years (22% to 41%, P < .001), but the frequency of smoke or smokers (13% and 10%, respectively, at baseline) did not change. According to employees interviewed at 24 months, 38% of stores illegally permitted customers or employees to smoke. These stores had more smoke and fewer signs than did stores prohibiting smoking. Compliance was poor in liquor and convenience stores. Employees who had been told how to handle customers' smoking were more likely to enforce the law. CONCLUSIONS. Compliance with a no-smoking law is not guaranteed. For retail stores, compliance may improve if stores adopt no-smoking policies, post signs, and teach employees to enforce the law.