The responses of 387 smokers and 988 nonsmokers obtained in a population-based survey in Ontario, Canada, were compared with regard to knowledge, attitudes, and predicted behavior concerning restrictions on smoking. Responses were tabulated as percentages and weighted according to the sample design. Nonoverlapping 95% confidence intervals provided evidence to reject the null hypothesis. Although smokers were found to be less knowledgable about the health effects of smoking and environmental tobacco smoke, more than 90% of both smokers and nonsmokers agreed with restrictions on smoking in 14 specific settings; for some settings, they disagreed on the extent of restrictions. The groups differed concerning specific bans on cigarette sales, but support was uniformly strong for bans in hospitals, controls on vending machines, and enforcement of the law prohibiting sales to minors. Clear majorities of both groups agreed that local government should enact and enforce restrictions. Smokers were more likely than nonsmokers to predict that smokers would comply with more restrictions, and most smokers indicated that they, themselves, would comply. We conclude that general health education should be bolstered by strategies specifically targeted at smokers. There is a strong basis across the population for restrictions to reduce exposure to environmental tobacco smoke; support for the role of local government in this regard is clear. Noncompliance with more restrictions is unlikely to present enforcement problems. Measures limiting the physical access of youths to tobacco will be widely supported, but strategies to increase support for tax measures are needed.