The aim of the present study was to evaluate the efficacy of treatment with recombinant interferon (IFN)-alpha2b in 12 children with chronic hepatitis B who had previously undergone therapy for cancer. Nine children had acute leukemias and the other three children had solid tumors. The mean (+/-SD) age of the children was 8.4+/-3.8 years (range 4-16 years). All cases were hepatitis B virus (HBV)-DNA positive and 11 were hepatitis B e antigen (HBeAg) positive. One was anti-HBe positive (mutant strain). Four cases were anti-delta IgG positive. Liver biopsy revealed chronic hepatitis B in 11 patients and cirrhosis in one patient. Interferon-alpha2b was given at a dose of 5 MU/m2 three times a week, subcutaneously, for 12 months. Elimination of serum HBV-DNA was obtained in three cases, but a further three patients demonstrated a marked decrease in HBV-DNA levels after therapy. Three of 11 patients seroconverted from HBeAg to anti-HBe. Alanine aminotransferase (ALT) levels returned to normal in three of nine cases in whom the ALT levels were high before treatment. At the end of therapy, the mean histologic activity index score was significantly diminished (P = 0.0039). In conclusion, a 12 month course of IFN-alpha2b induces some beneficial effects on virologic, biochemical and histologic indices in children with chronic hepatitis B who have previously undergone therapy for cancer.