We examined the feasibility of hepatitis C treatment in patients on opioid maintenance. One hundred patients with chronic hepatitis C, 50 on methadone maintenance, and 50 with no intravenous drug use or opioid maintenance for at least 5 years were prospectively matched for sex, age, hepatitis C virus (HCV) genotype and HCV RNA. The primary end point was undetectable HCV RNA at 24 weeks posttreatment. Treatment with peginterferon alfa-2b (1.5 microg/kg per week) and ribavirin (1000-1200 mg /day) was initiated for 24 weeks (HCV genotype 2, 3) or 48 weeks (HCV genotype 1, 4). Within the first 8 weeks of therapy, discontinuation due to noncompliance or patient request was observed in 22% (11/50) in the methadone group versus 4% (2/50) in the control group (P =.02). After 8 weeks, there was no significant difference in discontinuation due to noncompliance or patient request (4/39 [10%] vs. 4/48 [8%]). There was no difference in discontinuation of therapy because of viral failure or adverse events (10/50 methadone vs. 6/50 control, P =.41). At the end of treatment, 50% (25/50) in the methadone group and 76% (38/50) in the control group had undetectable HCV RNA (P =.01). Sustained viral response was 42% (21/50) in the methadone group and 56% (28/50) in the control group (P =.16). No serious psychiatric event occurred in either group. In conclusion, peginterferon and ribavirin seem reasonably safe and sufficiently effective in patients on methadone maintenance. Patients discontinuing therapy due to noncompliance or request did so early, thereby limiting the cost of an unsuccessful approach to treatment.