BACKGROUND: Though patients in opiate substitution programs are commonly infected with HCV, due to safety and efficacy concerns, they are rarely treated with interferon and ribavirin. METHODS: In a multicenter study, HCV-infected patients in opiate maintenance treatment programs received 180 microg pegylated interferon-alfa-2a once weekly, plus daily ribavirin for 24 weeks (genotypes 2, 3), or 48 weeks (genotypes 1, 4). RESULTS: Of the 67 patients enrolled, 31 (46%) had HCV genotypes 1 or 4, and 36 (54%) had genotypes 2 or 3. Intent-to-treat analysis showed end-of-treatment virologic response in 75% of patients (81% of genotypes 2 or 3; 65% of genotypes 1 or 4), and a sustained virologic response in 61% of patients (72% of genotypes 2 or 3; 48% of genotypes 1 or 4). Fifteen patients (22%) did not complete the study, in 5 (8%) cases because of severe adverse events. CONCLUSIONS: Drug users with chronic HCV infection, regularly attending an opiate maintenance program in which close collaboration between hepatologists/internists and addiction specialists is assured, can be treated effectively and safely with pegylated interferon-alfa-2a and ribavirin. Treatment results are very similar to those in other patient groups, and thus therapy should also be considered for this population.