Rituximab (MabThera, Rituxan is an anti-CD20 monoclonal antibody that induces lysis and apoptosis of normal and malignant human B cells, and sensitizes malignant B cells to the cytotoxic effect of chemotherapy. In phase III trials in patients with indolent or aggressive B-cell non-Hodgkin lymphoma (NHL), intravenous rituximab in combination with chemotherapy was more effective as first- or second-line therapy than chemotherapy alone in terms of tumor remission and patient survival. Likewise, in patients with chronic lymphocytic leukemia (CLL), rituximab in combination with chemotherapy appeared more effective than chemotherapy alone as either first- or second-line treatment. In addition, rituximab maintenance therapy was shown to significantly prolong tumor remission and patient survival in patients with indolent B-cell NHL or CLL. The combination of rituximab with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) was cost effective as first-line therapy for advanced-stage diffuse large B-cell NHL compared with CHOP alone. Rituximab, either alone or in combination with chemotherapy, was generally well tolerated in patients with NHL or CLL. Overall, rituximab in combination with chemotherapy, is a valuable option for first- and second-line therapy in patients with advanced-stage indolent or aggressive B-cell NHL, and possibly those with B-cell CLL, and is included in current treatment guidelines for these indications. The drug is also potentially useful as maintenance therapy in patients with indolent B-cell NHL or CLL.