A 62-year-old Japanese man who was positive for hepatitis B surface antigen (HBsAg) and anti-HBe antibody, underwent chemotherapy for non-Hodgkin's lymphoma (NHL). Mutations were detected in the precore region (nt1896) of HBV. Because steroid-containing regimen may cause reactivation of hepatitis B virus (HBV) and hepatitis may progress to be fulminant after its withdrawal, we administered CHO (CPA, DOX and VCR) therapy and the patient obtained complete response. However, he developed acute exacerbation of hepatitis due to HBV reactivation. Recovery was achieved with lamivudine (100 mg/d) and plasma exchange. The present case suggests that acute exacerbation of hepatitis can occur with steroid-free regimen. Because the efficacy of the prophylactic use of lamivudine has been reported and the steroid enhances curability of malignant lymphoma, the steroid containing regimen with prophylaxis of lamivudine should be evaluated further.