Patients admitted to a state psychiatric facility were interviewed to ascertain the co-occurrence of mental illness and chemical abuse (MI/CA), lifetime substance use, childhood experiences, current living conditions, and use of mental health services. Of the sample, 49% currently had MI/CA, and 20% more had used multiple substances. MI/CA patients were more likely to have been exposed to multiple early risk factors for substance use, including familial substance abuse, mental illness, and physical abuse. They were also younger, male, and experienced more adult homelessness, legal trouble, and family conflict. These results demonstrate the continuing need to develop MI/CA programs.