Exposure to secondhand smoke from burning tobacco products causes stroke, lung cancer, and coronary heart disease in adults (1,2). Children who are exposed to secondhand smoke are at increased risk for sudden infant death syndrome, acute respiratory infections, middle ear disease, more severe asthma, respiratory symptoms, and slowed lung growth (1,2). Secondhand smoke exposure contributes to approximately 41,000 deaths among nonsmoking adults and 400 deaths in infants each year (2). This report updates a previous CDC report that evaluated state smoke-free laws in effect from 2000-2010 (3), and estimates the proportion of the population protected by comprehensive smoke-free laws. The number of states, including the District of Columbia (DC), with comprehensive smoke-free laws (statutes that prohibit smoking in indoor areas of worksites, restaurants, and bars) increased from zero in 2000 to 26 in 2010 and 27 in 2015. The percentage of the U.S. population that is protected increased from 2.72% in 2000 to 47.8% in 2010 and 49.6% in 2015. Regional disparities remain in the proportions of state populations covered by state or local comprehensive smoke-free policies, as no state in the southeast has a state comprehensive law. In addition, nine of the 24 states that lack state comprehensive smoke-free laws also lack any local comprehensive smoke-free laws. Opportunities exist to accelerate the adoption of smoke-free laws in states that lack local comprehensive smoke-free laws, including those in the south, to protect nonsmokers from the harmful effects of secondhand smoke exposure.