In rituximab-containing regimen for lymphoma, the role of lamivudine therapy has not been well established. Therefore, in this nonrandomized phase II clinical study, hepatitis B virus (HBV) carriers with B-cell lymphoma who received rituximab-containing regimen were treated with oral administration of lamivudine. The incidence and severity of hepatitis along with other adverse clinical outcomes were analyzed. Between January 2003 and March 2006, 29 consecutive patients were enrolled. Four of the 29 patients (13.8%) developed hepatitis during chemotherapy, none of which was attributed to HBV reactivation. According to WHO acute toxicity assessment criteria, the severity of hepatitis was grade I in two patients (6.9%) and grade II in two patients (6.9%). In these four patients, only one (3.5%) had interval delay in chemotherapy. No patient had total abnormal bilirubin. No patient had died as the result of hepatitis during the treatment. Interestingly, one of the 29 patients developed HBV activation 5.1 months after the withdrawal of lamivudine. This patient recovered after reinstallation of lamivudine therapy and is still alive. Consequently, our study confirmed previous reports that prophylactic lamivudine therapy can prevent HBV reactivation in HBV carriers who were receiving rituximab-containing regimen for lymphoma.