Monoclonal antibodies (MoAb) conjugated with radioisotopes, i.e., I-131, Y-90, T-99, or In-111. Using radioimmunoconjugates in radiotherapy or radioimaging has the advantage of targeting cells carrying specific antigens, thereby limiting toxic effects on normal cells. Tumor eradication can be achieved by either the antibody-mediated immune response or by only the cytotoxic activity of the radiation.