OBJECTIVES: Most studies establishing the role of antiviral therapy in patients with chronic hepatitis C (CHC) excluded the patients with normal ALT levels. Small trials with interferon monotherapy suggested a limited efficacy and/or de novo ALT elevations. We sought to evaluate the efficacy of two doses of interferon alpha-2b (IFN) with ribavirin (RBV) in patients with normal ALT. METHODS: Patients with biopsy-proven CHC with detectable HCV RNA and at least two normal ALT levels three or more months apart were randomized to receive either 3 or 5 million units of IFN thrice a week plus RBV 1,000-1,200 mg. Therapy was stopped at 24 wk if HCV RNA remained detectable and continued for an additional 24 wk if HCV RNA was undetectable. A final HCV RNA level was obtained 24 wk after discontinuation of therapy. RESULTS: Fifty-six patients were randomized and received at least one dose of treatment. The overall rate of sustained virologic response (SVR) was 32%. SVR rates were higher in genotype 2 and 3 patients (80%) than in genotype 1 patients (24%, p = 0.002). There was a tendency toward higher SVR in genotype 1 patients treated with the higher IFN dose (36% vs 10%, p = 0.07). Five patients had mild, transient ALT elevations. No sustained ALT elevations were noted. CONCLUSIONS: Patients with normal ALT had a rate of SVR comparable to that reported in patients with elevated ALT. Higher dose of interferon tended to be more effective in genotype 1 infected patients. De novo ALT elevations were transient and not clinically significant. Patients with CHC should not be excluded from treatment on the basis of ALT alone. Combination therapy with pegylated interferon and ribavirin should be evaluated in these patients.