One hundred and twenty six patients were enrolled in a study to assess the effect of different interferon alfa-2b treatment regimens on the rate of increase in alanine aminotransferase (ALT) activities after treatment. Results indicated that a high daily dosage of interferon (10 million units (MU)) given six times a week for two weeks followed by 12 weeks of thrice weekly dosing was more effective at producing sustained normal ALT values than either eight weeks of 10 MU interferon six times a week or four weeks of 10 MU six times a week followed by eight weeks of thrice weekly dosing. Multiple regression analysis of clinical parameters before treatment showed that the outcome was dependent upon treatment group (p < 0.001) and the initial hepatitis C virus (HCV)-RNA value (p < 0.05). Anti-HCV titre and liver histology had a considerable but not significant effect on the response to treatment. The most frequently observed side effect was flu like syndrome, which occurred in over 90% of patients. In addition, 21% of patients experienced some degree of hair loss. Treatment was stopped because of side effects in 11 of 126 (9%) patients, evenly distributed between the three groups.