Clean indoor air laws are easily implemented, are well accepted by the public, reduce nonsmoker exposure to secondhand smoke, and contribute to a reduction in overall cigarette consumption. There are currently thousands of clean indoor air laws throughout the Unites States, and the majority of Americans live in areas where smoking is completely prohibited in workplaces, restaurants, or bars. The vast majority of scientific evidence indicates that there is no negative economic impact of clean indoor air policies, with many studies finding that there may be some positive effects on local businesses. This is despite the fact that tobacco industry-sponsored research has attempted to create fears to the contrary. Further progress in the diffusion of clean indoor air laws will depend on the continued documentation of the economic impact of clean indoor air laws, particularly within the hospitality industry. This article reviews the spread of clean indoor air laws, the effect on public health, and the scientific evidence of the economic impact of implementation of clean indoor air laws.