One hundred American Indian patients with a Psychoactive Substance Use Disorder (PSUD) were studied with special reference to associated psychiatric disorders. This clinical sample was divided into three groups: PSUD only, PSUD plus an Organic Mental Disorder (OMD), and PSUD plus any other psychiatric disorder. OMD diagnoses included primarily Delirium Tremens and Alcoholic Hallucinosis; cases of Alcohol Amnestic Disorder, Alcohol Dementia, and trauma-induced OMD were also encountered. Other psychiatric disorders included primarily Major Depression and Anxiety Disorder, with smaller numbers of Schizophrenia, Conduct, Sexual, and other Disorders. Demographic and clinical characteristics were compared among these three groups. Those with PSUD + OMD tended to be older, male, and have more DSM-III Axis 3 disorders (American Psychiatric Association 1980) as compared to other patients; those with PSUD + other diagnoses tended to be single and younger. Education and occupational status were not related to the three diagnostic groups. The data were also subjected to MANOVA analysis. Even when corrected for sex, types of substance being abused, Axis 3 health status, and other factors, the three diagnostic groups still bore a significant relationship to age. Those with PSUD + Other psychiatric diagnoses besides OMD tended to be youngest. Those with PSUD-only were intermediate by age, while those with PSUD + OMD tended to be the oldest.