The lifetime prevalence of specific DSM-III-defined psychiatric disorders among 1243 Mexican-American and 1309 non-Hispanic white residents of two Los Angeles communities is reported from the Los Angeles site of the Epidemiologic Catchment Area (ECA) research study. Results from household interviews in response to the National Institute of Mental Health Diagnostic Interview Schedule revealed overall rates of disorders for the total Los Angeles sample and ethnic subsamples that were similar to rates reported from the initial three ECA sites. Non-Hispanic whites reported far more drug abuse/dependence and more major depressive episodes than Mexican Americans. Young non-Hispanic white women reported high rates of major depressive episodes and drug abuse/dependence. Alcohol abuse/dependence is highly prevalent among Mexican-American and non-Hispanic white men of any age. Mexican-American women infrequently abuse or become dependent on drugs or alcohol at any age. Dysthymia, panic disorder, and phobia are somewhat more prevalent among Mexican-American women over 40 years of age compared with both non-Hispanic white women over and Mexican-American women under 40 years of age. Antisocial personality is predominantly a disorder of young men of both ethnic groups.