Jay S. Loeffler and Helen A. ShihDepartment of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School (J.S.L., H.A.S.), Boston, Massachusetts 02114Address all correspondence and requests for reprints to: Helen A. Shih, M.D., M.S., M.P.H., Massachusetts General Hospital, 100 Blossom Street, Cox 3, Boston, Massachusetts 02114.Context: Optimal management of pituitary adenomas involves consideration of the roles of medical therapy, surgery, and radiation therapy. The different forms of radiation therapy and their results are reviewed here.Evidence Acquisition: A literature search through the U.S. National Library of Medicine was used to identify and review clinical experiences of radiation therapy in the management of pituitary adenomas. Emphasis was placed on studies within the last 5–10 yr, with 5 or more years of follow-up data, and of reasonable quality of data. Older studies with larger numbers or particular significance are also highlighted.Evidence Synthesis: Success of radiation therapy in controlling tumor growth is high, 90–100% in most series, regardless of radiation technique and adenoma subtype. Success in achieving hormonal normalization in secretory tumors is more variable because of differences in patient population, radiation technique, and doses employed and variation of the definition of success. Complete biochemical remission is generally achieved in 50% of patients at 10 yr after treatment for most adenomas. Higher rates of normalization can be achieved with additional medical therapy. Hypopituitarism is an expectant result of radiation therapy. Overall rate of other treatment-related adverse effects is low.Conclusions: Radiation therapy should be considered in the management of patients with pituitary adenomas, particularly when medical and surgical options have been exhausted. Because response evolves slowly over many years and because hypopituitarism is likely to occur, patients should be counseled on the importance of continued endocrinological surveillance and medical management.