The authors retrospectively reviewed 50 episodes of spinal epidural tumor that occurred in 42 patients with metastatic prostate cancer and were treated with external-beam radiation. Treatment response was evaluated in terms of symptoms, neurologic status, and, in most cases, reduction of tumor on repeat myelography. At the completion of therapy, 92% of treated patients experienced pain relief and 67% had significant to complete improvement on neurologic examination. Thirty days after treatment, repeat myelography was performed in 40 of the 50 cases; compared with the initial findings immediately preceding radiation therapy (RT), the results of 58% of these studies had normalized completely, results were improved in 25%, and the results had not changed in 18%. The presence of a high-grade compression fracture of the vertebral body was an indicator of poor prognosis for tumor response on repeat myelography. The ability of a patient to walk before treatment and tumor response on repeat myelography were associated significantly with improved outcome of RT and with survival. The authors conclude that RT can effectively palliate epidural lesions from metastatic prostate cancer. The prognosis for the long-term response to therapy may be indicated by pretreatment ambulatory status and posttreatment imaging of the epidural space.