The survival, patterns, and mechanisms of failure in 171 patients with pure testicular seminoma treated with megavoltage irradiation from 1950 to 1976 were analyzed. The survival of the entire group was 93% at five and ten years post-irradiation. Survival at five years was significantly less for Stages III and IV (45%) when compared with Stages I and II (95%, P less than 0.001). Extranodal relapses were more common in early stages, and abdominal recurrences occurred in more advanced stages. Salvage treatment, management of HCG-producing seminomas, and second testicular seminomas are analyzed. The need for aggressive and appropriate radiation technique is emphasized.