BACKGROUND & AIMS: Patients with chronic hepatitis C and persistently normal alanine aminotransferase (ALT) levels have been routinely excluded from large randomized treatment trials; consequently, the efficacy and safety of antiviral therapy in this population are unknown. METHODS: Patients with at least 3 normal ALT values over an 18-month period were randomized (3:3:1) to treatment with peginterferon alfa-2a 180 mug/wk plus ribavirin 800 mg/day for 24 weeks (212 patients), the same combination for 48 weeks (210 patients), or no treatment (69 patients) in a multinational study. All patients were monitored for 72 weeks. The primary measure of efficacy was sustained virologic response (SVR), defined as undetectable serum hepatitis C virus (HCV) RNA by qualitative polymerase chain reaction at the end of 24 weeks of untreated follow-up. RESULTS: No patient cleared HCV RNA in the untreated control group. SVR rates of 30% and 52% were obtained in the 24- and 48-week treatment groups, respectively. In patients infected with HCV genotype 1, SVR rates of 13% and 40% were obtained with 24 and 48 weeks of treatment, respectively (P < .0001). In patients infected with genotypes 2 or 3, SVR rates were 72% and 78% with 24 and 48 weeks of treatment, respectively (P = .452). Treatment-related flares in ALT activity were not observed. CONCLUSIONS: The efficacy and safety of peginterferon alfa-2a and ribavirin combination therapy in patients with chronic hepatitis C and persistently normal ALT levels are similar to that in patients with elevated ALT levels. The indication for treatment of hepatitis C can be evaluated independently from baseline ALT activity.