Multiple studies have reported about substance abuse in Blacks and Hispanics. However, little is known about substance-abusing psychiatric patients of these ethnic groups. This study reports the prevalence and patterns of substance abuse among 171 consecutive patients (90 Blacks and 81 Hispanics) admitted to the acute psychiatric unit of an inner-city general hospital. The lifetime prevalence was 63%. Within the month prior to admission, 48% had used the following substances: cannabis, 40%; alcohol, 37%; amphetamines, 20%; cocaine, 12%; phencyclidine (PCP), 12%; barbiturates and/or sedative-hypnotics, 10%; opioids, 9%; inhalants, 1%; hallucinogens, 1%. Those who abused alcohol were more likely to abuse barbiturates and/or sedative-hypnotics, and opioids. Logistic regression analysis showed that major depression, ethnicity, and schizophrenia each were significant predictors of particular types of abuse. Patients with major depression were less likely to use PCP, Blacks were more likely than Hispanics to use hallucinogens, and schizophrenics were less likely to use opioids. In all cases in which sex, age, and personality disorder were significant, males, the young adult group, and those with personality disorder were more likely to be abusers. These three variables were all strong predictors of both multiple and extensive substance abuse. Overall, our findings suggest that in the inner-city, a substantial number of young adult psychiatric inpatients are a high risk group for multiple substance abuse. The coexistence of substance abuse and other psychiatric disorders has clinical and treatment implications, and calls attention for changes within the conventional psychiatric milieu.