Radioimmunotherapy (RIT) treatment for lymphoma is a novel targeted therapeutic approach. Several years of development of radioimmunotherapeutic compounds came to fruition in February of 2002 when the US Food and Drug Administration (FDA) approved yttrium 90 ((90)Y)-ibritumomab tiuxetan ((90)Y-IT) for the treatment of relapsed or refractory, low-grade, or transformed B-cell lymphoma. (90)Y-IT uses a monoclonal anti-CD20 antibody to deliver beta-emitting (90)Y to the malignant B cells. Clinical trials have demonstrated its efficacy, which is largely independent of the intrinsic activity of the anti-CD20 antibody. A similar anti-CD20 radiotherapeutic compound, iodine 131 ((131)I)-tositumomab ((131)I-T), is also under consideration for approval. The advantages of increased efficacy compared to the native antibody are gained at the expense of myelotoxicity, which is dose-limiting but reversible. Other radioimmunoconjugates (RIC), including products for Hodgkin's lymphoma, are in earlier stages of development. Studies exploring expanded applications of RIT are under way. RIT has been shown to be an effective and clinically relevant complementary therapeutic approach for patients with lymphoma.