Understanding the trends in the prevalence of cigarette smoking among youths enables policy makers to target prevention resources more effectively. Every 2 years, CDC analyzes data from the national Youth Risk Behavior Survey (YRBS) to evaluate trends in cigarette use among high school students in the United States. This report updates a previous report and describes results of CDC's 2010 analysis of YRBS data from 1991-2009 for three measures: ever smoked cigarettes, current cigarette use, and current frequent cigarette use. For ever smoked cigarettes, the prevalence did not change from 1991 (70.1%) to 1999 (70.4%), declined to 58.4% in 2003, and then declined more gradually, to 46.3% in 2009. For current cigarette use, the prevalence increased from 27.5% in 1991 to 36.4% in 1997, declined to 21.9% in 2003, and then declined more gradually, to 19.5% in 2009. For current frequent cigarette use, the prevalence increased from 12.7% in 1991 to 16.8% in 1999, declined to 9.7% in 2003, and then declined more gradually, to 7.3% in 2009. For all three measures, rates began to decline in the late 1990s, but the rate of decline slowed during 2003-2009. To increase the rate of decline in cigarette use among high school students, reductions in advertising, promotions, and commercial availability of tobacco products should be combined with full implementation of communitywide, comprehensive tobacco control programs.