Twelve children with chronic non-A, non-B hepatitis were entered in a pilot trial of recombinant interferon-alpha. Although all the children had hepatitis C virus RNA in serum, only five had antibodies against this virus. Children received 3 MU/m2 body surface area interferon-alpha 3 times/wk for 6 mo; they were followed for 24 mo, including the therapy period. One child was dropped from the study, so the results are from the 11 children who completed the study. At the end of the therapy period, 36% of the children had normal ALT levels; this percentage increased to 90% at mo 15 of follow-up. Thereafter, relapse occurred in five children; thus ALT normalization was observed in 5 of 11 children at the 24th month. Moreover, two different ALT patterns were found: HCV antibody-negative children had significant peaks of ALT levels with respect to the basal samples (p less than 0.05) until the third month of the therapy; these levels later decreased. In contrast, HCV antibody-positive children had slight fluctuations of ALT until normal levels were reached. At the end of treatment, three children had HCV RNA; one demonstrated a rebound in ALT levels. Finally, histological activity had decreased significantly in the second liver biopsy specimen in all children. In summary, interferon treatment in children with chronic hepatitis C may be helpful, although these results should be confirmed in controlled trials.