Despite advances in the therapy of chronic hepatitis C, a large number of patients do not respond to current therapies. The study objective was to assess whether a combination of interferon (IFN) alfacon-1 and ribavirin improves the response rate compared with a combination of INF alpha-2b and ribavirin in chronic hepatitis C subjects. The study was designed as an open-label, prospective, randomized, controlled study; 128 subjects with chronic hepatitis C were randomized to INF alfacon-1, 15 microg three times per week, plus ribavirin, 1 g/day, or IFN-alpha2b, 3 million units three times per week, plus ribavirin, 1 g/day for 48 weeks. The end point of the study was a sustained viral response, defined as undetectable HCV RNA at 24 weeks post 48 weeks of treatment. Overall, 57% of subjects in the INF alfacon-1/ribavirin group achieved a sustained antiviral response, compared with 40% of subjects in the IFN-alpha2b/ribavirin group (P = 0.052). In the subset of subjects with a high viral load, HCV RNA was successfully eradicated in more individuals who received INF alfacon-1/ribavirin than subjects who received IFN-alpha2b/ribavirin (57 versus 31%; P = 0.025). Among individuals with genotype 1 and a high viral load, the sustained antiviral response was significantly higher with INF alfacon-1/ribavirin than with IFN-alpha2b/ribavirin (46 versus 14%; P = 0.019). Adverse events were similar in both treatment groups. In conclusion, this study demonstrated that the combination of INF alfacon-1 and ribavirin provides a significantly better treatment response compared with the combination of IFN-alpha2b and ribavirin in chronic HCV subjects infected with genotype 1 and a high viral RNA load.