The use of monoclonal antibodies (MAbs) as radiation carriers in argeted radiotherapy of cancers has produced striking clinical responses in hematologic diseases, such as non-Hodgkin's lymphoma. Novel strategies are currently being examined in an effort to improve efficacy in solid tumor therapies. Two of these strategies involve minimizing the systemic toxicity of a circulating radionuclide via 'pretargeting', and the sensitization of tumors to radiation by combination therapy with radiosensitizing drugs. Advances made in radiolabeling chemistries and in the use of alpha-particle emitters can also improve utility. Clinical evidence suggests that radioimmunotherapy may be best applied in minimal-disease and adjuvant settings in combination with other cancer therapy modalities.