The availability of monoclonal antibodies with well-defined specificities to lymphoma-associated antigens promises to open new therapeutic opportunities in the treatment of patients with non-Hodgkin's lymphoma. Monoclonal antibodies against lineage-specific surface markers such as CD19, CD20 or CD22 have been generated and employed in native or modified forms in clinical phase I/II trials. Modified versions such as toxin-conjugated antibodies or antibodies with dual specificities (bispecific antibodies) were introduced to enhance the cytotoxicity of monoclonal antibodies since native antibodies were not able to induce long-lasting remissions in patients with advanced disease although responses were seen and side-effects were usually mild. Future efforts should concentrate on patients with minimal residual disease employing genetically engineered antibody fragments.