We have evaluated the efficacy of treatment with recombinant Interferon-2b (IFN-2b) in 12 children with cancer who developed chronic hepatitis-B infection, Seven of them had lymphoblastic leukaemia and others had solid tumours, Seven cases were male. Mean age was 10.5 years with a range of 5-16 years. Chronic Hepatitis B was diagnosed biochemically, serologically and histopathologically. They were HBsAg(+), NBV-DNA(+), and HCV(-), HIV(-). Seven cases were HBeAg(+) and two of them were anti-Delta IgG(+), Liver biopsy revealed chronic active hepatitis in six cases and persistent hepatitis in three eases. IFN rues given at the dose of 5 MU/m(2) three times a week, subcutaneously for 6 months. It was well tolerated, After IFN therapy, ALT levels returned to normal in seven cases, All cases were still BBsAg(+). Four of them seroconverted to anti-HBe antibody. Loss of serum HBV-DNA in three cases, but 11 cases showed a marked decrease after IFN, The control liver biopsies showed that histopathological activity index was diminished in five cases. Other 16 patients, serving as control, received no therapy. Five of them were leukaemia and others were solid tumours. Twelve cases were male, Mean age was 9.3 years with a range of 4-19 years. After 6 months, only one patient lost HBV-DNA and three of them seroconverted to anti-HBe with normalization of ALT values.