dSecondhand smoke (SHS) causes premature disease and death in nonsmokers, including heart disease and lung cancer. The Surgeon General has concluded that no risk-free level of SHS exposure exists; the only way to fully protect nonsmokers is to completely eliminate smoking in indoor spaces. Studies have determined that levels of airborne particulate matter in restaurants, bars, and other hospitality venues and levels of SHS exposure among nonsmoking hospitality employees decrease substantially and rapidly after implementation of laws that prohibit smoking in indoor workplaces and public places. To assess changes in indoor SHS exposure in a general population, the New York State Department of Health analyzed data on observations of indoor smoking by respondents to the New York Adult Tobacco Survey (NYATS) and measured levels of cotinine in saliva among nonsmoking NYATS respondents before and after implementation of the 2003 New York state ban on smoking in indoor workplaces and public places. This report describes the results of that analysis, which determined that reports of indoor smoking among restaurant and bar patrons decreased significantly after the law took effect; moreover, saliva cotinine levels in nonsmoking NYATS participants decreased by 47.4% over the same period. These findings suggest that comprehensive smoking bans can reduce SHS exposure among nonsmokers.