This review discusses the current limitations and future prospects of radiolabeled antibodies in cancer imaging (radioimmunodetection, or RAID) and therapy (radioimmunotherapy, or RAIT). Aspects such as the antibody vehicle, antigen target, radiolabel, tumor, host, and RAID and RAIT procedures are considered. In the short timespan for the development of RAID, tumors as small as 0.5 cm, which are sometimes missed by other radiological methods, can now be imaged with antibody fragments labeled with suitable radionuclides (eg, 111In, 123I, and 99mTc), particularly when single photon emmission computed tomography (SPECT) scanning methods are employed. 99mTc is clearly the preferred label, and the recent development of simple and rapid methods to attach this isotope to antibodies should be a welcome advance for the more widespread use of RAID. In RAIT, radiosensitive neoplasms, such as lymphomas, are already showing impressive responses to 131I-labeled antilymphoma murine monoclonal antibodies. Therefore, the successful conjugation of beta- and alpha-emitters to "humanized" monoclonal antibodies should provide a new generation of promising cancer therapeutics.