Radioimmunotherapy and antibody-directed chemotherapy have emerged as cancer treatment modalities with the regulatory approval of products for non-Hodgkin's lymphoma and acute myeloid leukemia. Antibody-toxin therapy is likewise on the verge of clinical fruition. Accumulating evidence suggests that radioimmunotherapy may have the best impact in minimal-disease and adjuvant settings, especially with radioresistant solid tumors. For the latter, ongoing efforts in 'pretargeting' to increase deliverable tumor radiation dose, combination therapies, and locoregional applications are also of importance. Antibody-drug conjugates have the potential to increase the therapeutic index of chemotherapy by minimizing systemic toxicity and improving tumor targeting. The design of optimal drug conjugates in this regard is predicated upon the proper choice of the target antigen, the cleavable-linker, and the drug. In respect of antibody-toxin conjugates, considerable progress has been made in chemical and recombinant immunotoxin designs, and in the advancement of many products to clinical trials. Continued development of antibody-directed therapies should expand the options available for the management of cancer.