Six patients with chronic hepatitis C who were cured of malignancy were treated with recombinant interferon-alpha at the dose of 4 MU/m2 for 12 months; the post-treatment follow up period was 12 months. Therapy was stopped within 6 months in three patients because of persistently abnormal alanine aminotransferase levels. In the remaining three patients, a complete normalization of alanine aminotransferase levels was obtained during treatment but it was not maintained after the end of interferon therapy. In addition, no patient cleared hepatitis C virus ribonucleic acid in serum. These results suggest that recombinant interferon is not effective in patients with chronic hepatitis C who were cured of a previous malignancy.