At present standard treatment of patients with chronic hepatitis C is combined therapy with interferon-alpha and ribavirin which so far gives the best results. It is recommended in patients with resistance to interferon or a relapse after termination of treatment by interferon alone as well as in hitherto untreated patients. Combined treatment produces, however, not only common side-effects which are caused by interferon as well as ribavirin but rarely also serious side-effects produced by combined treatment which call for premature termination of therapy. The authors present an account on two patients who had serious side-effects during combined treatment: the first one was an intravenous drug addict who developed psychosis during combined treatment, the second one a female patient with cirrhosis and incipient portal hypertension who developed after nine months of combined treatment a severe biochemical relapse with jaundice, and treatment was also terminated. Both serious complications after treatment receded and in the first patient a sustained response to antiviral therapy persists for more than one year.