The study examined the ethnic ratio of 16 DSM-III mental disorders among White, Black, Hispanic, and Asian Americans. A total of 18,126 residents from 5 sites and 2,939 residents from the Epidemiological Catchment Area's Los Angeles site were studied separately. Logistic regression analysis was performed. Results showed that Blacks were significantly less likely than Whites to have major depressive episode, major depression, dysthymia, obsessive-compulsive disorder, drug and alcohol abuse or dependence, antisocial personality, and anorexia nervosa, but they were significantly more likely than Whites to have phobia and somatization. Lifetime prevalence rates of schizophrenia, obsessive-compulsive disorder, panic, and drug abuse or dependence were significantly lower among Hispanics than among Whites. Asians also had significantly lower rates than Whites of schizophreniform, manic episode, bipolar disorder, panic, somatization, drug and alcohol abuse or dependence, and antisocial personality. Compared with the overall findings, ethnic differences at the Los Angeles site were lessened between Blacks and Whites, enhanced between Hispanics and Whites, and basically unchanged between Asians and Whites.