An increasing number of U.S. states and communities have implemented smoke-free policies prohibiting smoking in all indoor workplaces and public areas. Public attitudes toward smoke-free environments are an evidenced-based, key indicator for the successful implementation and enforcement of smoke-free policies. Data were obtained from the 2009-2010 National Adult Tobacco Survey, a landline and cell phone survey of adults aged ≥18 years old residing in the 50U.S. states and the District of Columbia. The overall proportion of respondents who reported that smoking should "never be allowed" in workplaces, restaurants, and bars/casinos/clubs was calculated, both nationally and by state. National estimates were also calculated by sex, age, race/ethnicity, education, annual household income, sexual orientation, and smoking status. Nationally, 81.6% of U.S. adults think workplaces should be smoke-free (state range: 68.6% [Kentucky] to 89.1% [California]); 74.9% think restaurants should be smoke-free (state range: 59.5% [Missouri] to 84.6% [California]); 50.0% think bars/casinos/clubs should be smoke-free (state range: 32.3% [Nevada] to 61.3% [Maine]); and 47.5% think workplaces, restaurants, and bars/casinos/clubs should be smoke-free (state range: 30.3% [Nevada] to 58.8% [Maine]). Regardless of venue type, women, older individuals, non-Hispanic Asians, individuals with higher education and income, and nonsmokers were the most likely to think these environments should be smoke-free. A majority of U.S. adults think workplaces and restaurants should be smoke-free, while half think bars, casinos, and clubs should be smoke-free. Continued efforts are needed to educate the public about the dangers of secondhand smoke and the benefits of smoke-free indoor environments.