Federal probationers or parolees with a history of opioid addiction were referred by themselves or their probation/parole officer for a naltrexone treatment study. Participation was voluntary and subjects could drop out of the study at any time without adverse consequences. Following orientation and informed consent, 51 volunteers were randomly assigned in a 2:1 ratio to a 6-month program of probation plus naltrexone and brief drug counseling, or probation plus counseling alone. Naltrexone subjects received medication and counseling twice a week; controls received counseling at similar intervals. All therapy and medication were administered in an office located adjacent to the federal probation department. Fifty-two percent of subjects in the naltrexone group continued for 6 months and 33% remained in the control group. Opioid use was significantly lower in the naltrexone group. The overall mean percent of opioid positive urine tests among the naltrexone subjects was 8%, versus 30% for control subjects (p < .05). Fifty-six percent of the controls and 26% of the naltrexone group (p < .05) had their probation status revoked within the 6-month study period and returned to prison. Treatment with naltrexone and brief drug counseling can be integrated into the Federal Probation/Parole system with favorable results on both opioid use and re-arrest rates.