The goal of the National MMT Program is harm reduction for inmates addicted to heroin or other opiates. Phase I of the Program is designed to continue MMT for offenders who received methadone treatment in the community prior to their arrest. Phase I was modified to allow other addicted offenders into the program if their health is seriously compromised by their addiction. A group of 303 MMT offenders and a control group of 215 drug-addicted offenders not enrolled in the MMT Program were compared to assess the effectiveness of the National MMT Program in correctional facilities. Measures included recidivism rates and type of revocation among the two groups. Results revealed that, overall, the MMT group recidivated at a lower rate and at a slower pace than the comparison group. However, the results did not show a significant difference in the rate of new offenses for the two groups. Limitations of the evaluation include the fact that MMT offenders were not followed up in the community to find out if they continued their methadone treatment. Future evaluations should focus on other pre- and post-measures. CSC should consider changing the program criteria to allow offenders who have no prior methadone treatment into the MMT Program. Tables, notes