In a study of 87 patients with chronic hepatitis C, 12 months' treatment with interferon alfa-2b at a dose of 6 million units (MU) three times per week seemed to be more effective than treatment with 3 MU three times a week for two months plus 1.5 MU three times a week for 10 months in increasing the percentage of long term responders. The percentage of patients in whom alanine amino-transferase activities returned to normal was highest in the 6 MU group, as was the percentage of responders who sustained this normal activity after treatment. Side effects were moderate and self-limited in most patients.