Subjects participating in an IOT program at a community mental health center underwent descriptive testing at entry and at 6-month follow-up. Analysis of variance was used to compare subjects receiving carbamezapine, desipramine, or placebo on such variables as retention in treatment, days of treatment exposure, drug-free urine toxicology, and Addiction Severity Index (ASI) composite scores. Subjects demonstrated significant improvement in ASI scales over time, with an interaction effect of time and scale. Minimal interaction between psychiatric diagnosis and treatment outcome was observed. Although the IOT program was effective in reducing ASI composite scores, comparison with standard inpatient and outpatient treatment is recommended. 7 references, 3 tables, and 3 figures