OBJECTIVE The aims of this study were to determine 1) prevalence of leisure-time physical inactivity in a nationally representative sample of non-Hispanic white, non-Hispanic black, and Hispanic men and women; 2) prevalence of leisure-time inactivity by racial/ethnic group across social class indicators; and 3) the relationship between leisure-time inactivity and occupational physical activity, independent of other social class indicators. METHODS The National Physical Activity and Weight Loss Survey was a telephone survey of noninstitutionalized U.S. adults (4695 men, 6516 women) conducted by random digit dialing between September and December 2002. Self-reported physical activity was assessed using questions from the 2001 Behavioral Risk Factor Surveillance System. Respondents who reported no moderate- or vigorous-intensity physical activity during leisure time in a usual week were classified as inactive. Indicators of social class were education, family income, employment status, and marital status. RESULTS Age-adjusted prevalence of leisure-time inactivity was 9.9% +/- 0.6 SE (standard error) and 12.0 +/- 0.6 for white men and women, respectively; 19.0 +/- 2.5 and 25.2 +/- 2.1 for non-Hispanic black men and women, and 20.9 +/- 2.1 and 27.3 +/- 2.5 for Hispanic men and women. Within each racial/ethnic group, prevalence of leisure-time inactivity was highest among participants of lower social class. Differences in inactivity by racial/ethnic group were less evident after adjustment for social class. Odds of inactivity were similar across quartiles of occupational physical activity after adjustment for age, sex, and social class. CONCLUSIONS Non-Hispanic blacks and Hispanics were more inactive during their leisure time than were non-Hispanic whites. Social class but not occupational physical activity seems to moderate the relationship between race/ethnicity and leisure-time physical inactivity.