OBJECTIVE: An exploratory, cross-sectional study examined personal, clinical, and treatment characteristics among non-Hispanic Caucasian, non-Hispanic African American, and Hispanic indigent, inner-city clients with co-occurring disorders. METHODS: Men and women, 20-50 years old who met DSM-IV criteria for concurrent mood and substance use disorders were eligible. Inpatients, persons in detoxification programs, or incarcerated inmates were excluded. Assessments covered sociodemographic characteristics, clinical diagnoses, substance use, psychosocial variables, health care utilization and treatment history. RESULTS: Two hundred volunteers were screened, and 145 were eligible to enroll. Racial ethnic group differences in the distribution of mood and substance use disorders and medical diseases were evident. Receiving psychiatric treatment and psychiatric medications significantly differed among racial ethnic groups with Caucasians more likely to receive these services than African Americans or Hispanics. African Americans and Hispanics were also more likely than Caucasians to test positive for their drug of choice and for other drugs as well. Serious medical illnesses were evident in about half of the sample, and the distributions of these illnesses significantly differed among racial ethnic groups. There were no significant differences in hospitalization or emergency room visits among racial ethnic groups. CONCLUSIONS: Indigent, inner-city clients have multiple psychiatric and medical problems that warrant continuity of care. However, few doctor's visits for medical illnesses, lack of psychotropic medications, staggering unemployment, and homelessness were common in our sample. These results present healthcare and social service professionals with potentially serious treatment challenges. Better recognition and understanding of racial ethnic needs in those with co-occurring disorders are needed.