The increasing number of drug-involved offenders under the supervision of the criminal justice system offers a unique opportunity for HIV risk-reduction intervention. The article describes a 6-month work-release drug treatment program and the HIV risk factors of a cohort ordered by the court to attend. The treatment paradigm is the therapeutic community, and privileges and freedom increased as inmates progressed through the program. Inmates were followed up at 6, 18, and 42 months after program entry, and their HIV risk behaviors again assessed. The treatment cohort showed greater changes in risk behaviors compared to a cohort completing a similar work-release program without a treatment component. The program was effective in reducing three major HIV risk behaviors: intravenous drug use, trading sex for drugs, and inconsistent condom use. It was not effective in reducing one of the risk factors: the number of sex partners. Tables, references