Secondhand smoke (SHS) causes premature death and disease in children and nonsmoking adults. The home is the primary source of exposure to SHS for infants and children and a major source of SHS exposure for nonsmoking adults. To assess trends in national and state-specific prevalence of home "no smoking" rules (i.e., smoke-free home rules), CDC analyzed data from the Tobacco Use Supplement to the Current Population Survey for 1992-1993, 1998-1999, and 2003. This report summarizes the results of that analysis, which indicated that the national prevalence of households with smoke-free home rules in the United States increased significantly, from 43.2% during 1992-1993 to 72.2% in 2003. During this period, the national prevalence of such rules increased from 9.6% to 31.8% among households with at least one smoker and from 56.8% to 83.5% among households with no smoker. A regression analysis of the rate of change over time indicated that the increase in smoke-free homes during this period was not significantly different for households with at least one smoker compared with households with no smoker. Statistically significant increases in the prevalence of smoke-free home rules were also observed in all states, although variation was observed among states. Comprehensive tobacco-control measures, including 1) evidence-based interventions to help smokers quit, 2) policies making workplaces and public places smoke-free, 3) voluntary rules making homes smoke-free, and 4) initiatives to educate the public regarding the health effects of SHS, are needed to further reduce exposure of nonsmokers to SHS.