BACKGROUND Therapy options for patients with chronic hepatitis C who failed prior treatment are needed. In recent studies triple antiviral therapy with Interferon-alpha, ribavirin, and amantadine seemed to increase sustained virological response rates in this group. METHODS To evaluate efficacy, side effects and safety of a triple re-therapy in an open labeled prospective study, we compared 23 nonresponders to interferon monotherapy (9 nonresponders, 3 relapsers, 11 with breakthrough) with 23 nonresponders to standard combination therapy (interferon plus ribavirin) (16 nonresponders, 7 breakthroughs). All outpatients enrolled for re-therapy received interferon-alpha 2a (6 mega units [MU] three times in week), ribavirin (1000-1200 mg daily in divided doses) and amantadine (200 mg daily) for six months. In case of virological re-therapy response (negative qualitative HCV RNA) study medication was continued with interferon monotherapy for another six months. RESULTS Sustained virological response was achieved in 16 (35%) out of 46 prior therapy nonresponders. Response rates were dependent on pretreatment outcome. In the standard combination therapy group only 1 (6%) primary nonresponder achieved sustained response, but none of the 9 monotherapy nonresponders did. After primary breakthrough sustained response was seen in 8 of 11 (73%) patients in the interferon monotherapy and in 5 of 7 (71%) in the combination therapy group. Of 3 monotherapy relapsers 2 (66%) did also clear the virus sustained. Safety profile under triple therapy was similar to the previous therapy. Compliance was higher and side effects lower in those patients already experienced in combination therapy. CONCLUSIONS In patients with a breakthrough or relapse after interferon monotherapy or standard combination therapy with interferon and ribavirin a re-therapy with a triple combination of interferon, ribavirin, and amantadine results in a high rate of sustained virological response.