Ribavirin plus interferon-alpha (IFN alpha) combination has led to a marked advance in the treatment of IFN alpha-naive or relapser patients with chronic hepatitis C but was shown to be only marginally effective in IFN alpha-nonresponders. We therefore conducted a pilot study to see whether an intensified treatment protocol might be more effective in inducing a virological response in patients who had not responded virologically to previous IFN alpha monotherapy. 14 nonresponder patients with histologically proven chronic hepatitis C were included in the study. Patients received 9 MU IFN alpha-2a daily for one week followed by 9 MU IFN alpha every second day for further 5 weeks. With the beginning of the seventh week, patients were treated with 6 MU IFN alpha thrice in week (tiw) for a period of 6 weeks (until week 12). IFN alpha was continued up to 48 weeks at a dose of 3 MU IFN alpha tiw. Ribavirin (1000-1200 mg/day) and amantadine sulphate (200 mg/day) was given orally for 48 weeks. One patient discontinued therapy after first IFN alpha injection and one other patient after 12 weeks of therapy because of side effects. The remaining 12 patients completed treatment according to the protocol. An initial virological response at week 24 was achieved in 2 of the 14 patients (14%) and both patients remained HCV RNA negative at the end of treatment. However, both patients relapsed 4 weeks after completion of therapy, and therefore none of the patients achieved a virological sustained response. Viral dynamics studies showed a marked decline in hepatitis C viremia during the first 6 weeks of high-dose IFN alpha. After IFN alpha dose reduction, however, viremia stabilized or increased in most patients. These data indicate, that even triple therapy with high-dose IFN alpha plus ribavirin and amantadine fails to improve significantly the response rates in IFN alpha-nonresponders.