In the last years monoclonal antibodies directed against B-cell associated epitopes have enriched our armentarium of therapeutic strategies against malignant B-cell lymphoma. Monoclonal antibodies are characterized by a different mode of action compared to chemotherapy, thereby opening new avenues in lymphoma treatment. These monoclonal antibodies can exert their anti-lymphoma activity directly by an intrinsic cytotoxic effect or indirectly as a carrier of cytotoxic drugs or radioisotopes. Rituximab, an anti-CD20 monoclonal antibody, was proven to be highly active in indolent as well as aggressive lymphoma, in particular when combined with chemotherapy. The anti-CD52 antibody alemtuzumab was shown to induce remissions in high risk CLL. Furthermore, clinical trials have demonstrated promising activity of monoclonal antibodies conjugated to radioisotopes such as the (131)iodine anti-CD20 antibody tositumomab or the (90)yttrium anti-CD20 antibody ibritumomab tiuxetan.