We performed an independent meta-analysis of all available randomized clinical trials of interferon alfa-2b in patients with chronic hepatitis C. Articles published between 1986 and 1996 had to include previously untreated patients who were randomly allocated to therapy with at least 2 million units (MU) of interferon alfa-2b three times weekly for 24 weeks. A total of 32 trials met the inclusion criteria. Of these, 20 compared interferon-treated patients to placebo recipients or untreated patients and were used in the primary meta-analysis that compared rates of end-of-treatment and 6-month post-treatment sustained biochemical (normal alanine aminotransferase [ALT] levels) responses, end-of-treatment and 6-month sustained virological responses (absence of hepatitis C virus [HCV] RNA), and end-of-treatment histological responses in patients with paired biopsies. An additional 12 trials compared different doses, duration, or strategies of treatment. In comparison with no treatment, interferon alfa-2b therapy was associated with significant improvement in all end points measured. End-of- treatment biochemical responses were seen in 47% of treated patients compared with 4% of controls (odds ratio, 25.1; P < .0001). The biochemical responses were sustained for at least 6 months in 23% of treated patients compared with 2% of controls (odds ratio, 17.8; P < .0001). End-of-treatment virologic responses were observed in 29% of treated patients compared with 5% of controls (odds ratio, 9.4; P < .001) and 6-month sustained virologic responses were documented in 8% of treated patients compared with 1% of controls (odds ratio, 8.6; P < .001). Histological responses were recorded in 73% of treated patients compared with 38% of controls (odds ratio, 4.8; P < .0001). Extended therapy for 12 to 24 months resulted in significant improvement in 6- month sustained responses: 27% versus 14% (odds ratio, 2.9; P < .001). Higher dose therapy also resulted in modest increases in end-of- treatment (61% vs. 52%; odds ratio, 1.8; P < .02) and 6-month sustained responses (28% vs. 19%; odds ratio, 2.2; P < .01).