Among 262 inpatients with hematologic diseases who were referred for chemotherapy or immunosuppressive therapy between January, 1985, and December, 1989, nine (3.4%) patients, including two with Hodgkin's disease (HD), three with acute myeloblastic leukemia, one with chronic myelogenous leukemia, two with multiple myeloma and one with aplastic anemia, were found to be hepatitis B virus (HBV) carriers before their chemotherapy began. All six HBV carriers who received chemotherapy containing glucocorticoid showed mild-to-moderate elevations in serum transaminase levels after the chemotherapy. Five showed a rise in titer of the hepatitis B surface antigen, HBsAg. In contrast, three HBV carriers not receiving glucocorticoid showed no change in serum transaminase after chemotherapy. One HBV carrier with HD suffered from severe icteric hepatitis after the withdrawal of multiagent chemotherapy containing glucocorticoid. The HBV-DNA polymerase rose markedly and was accompanied by a marked rise in titer of HBsAg. The results warn us to keep in mind the possibility of glucocorticoid inducing an activation of HBV infection, which may result in severe hepatitis in some HBV carriers. Although further investigation is required, it is recommended that HBsAg-positive patients with hematologic malignancies should, if possible, be treated without glucocorticoid.