Poor mental health is a major source of distress, disability, and social burden; in any given year, as many as one in five adults in the United States has a mental disorder. To identify differences among populations and factors contributing to poor mental health, CDC examined the prevalence of frequent mental distress (FMD) among U.S. adults by race/ethnicity, socioeconomic status (SES), and sex, by using aggregate data from Behavioral Risk Factor Surveillance System (BRFSS) surveys for 1993-2001. This report describes the results of that analysis, which indicated that the prevalence of FMD varied among racial/ethnic populations and increased substantially among whites and blacks. In addition, FMD was reported more frequently by women and by persons with low SES within each racial/ethnic population. Targeting adverse socioeconomic risk factors and improving access to mental health services might decrease FMD among adults and reduce racial/ethnic disparities in mental health.