The chimeric anti-CD20 monoclonal antibody, rituximab, is a promising treatment for cutaneous B-cell lymphomas. Classically used in combination with a multiagent-chemotherapy regimen, it can sometimes give excellent results alone. Because of its selective action on B lymphocytes, it is considered a moderate immunosuppressant in terms of infection. We describe a woman with relapsed cutaneous follicular centre B-cell lymphoma and secondary lymph-node involvement treated with rituximab alone, which induced a complete remission. One year later, she experienced a fatal hepatitis B virus (HBV) reactivation. Several such HBV reactivations were reported after combined rituximab and multiagent chemotherapy for B-cell lymphomas. This is the first case of HBV reactivation occurring during the year following rituximab monotherapy in the absence of any other immunosuppressive factor.