This study examined the impact of prison-initiated methadone maintenance at 12 months postrelease. Males with pre-incarceration heroin dependence (N = 204) were randomly assigned to (a) Counseling Only: counseling in prison, with passive referral to treatment upon release; (b) Counseling + Transfer: counseling in prison with transfer to methadone maintenance treatment upon release; and (c) Counseling + Methadone: counseling and methadone maintenance in prison, continued in the community upon release. The mean number of days in community-based drug abuse treatment were, respectively, Counseling Only, 23.1; Counseling + Transfer, 91.3; and Counseling + Methadone, 166.0 (p < .01); all pairwise comparisons were statistically significant (all ps < .01). Counseling + Methadone participants were also significantly less likely than participants in each of the other two groups to be opioid-positive or cocaine-positive according to urine drug testing. These results support the effectiveness of prison-initiated methadone for males in the United States. Further study is required to confirm the findings for women.