Infradiaphragmatic radiotherapy remains the treatment of choice for patients with stage I and II (small volume) testicular seminoma. With this approach, the disease-free survival rate exceeds 90% to 95%, and the ultimate disease-free survival rate (including salvage) is 95% to 100%. Initial therapy for patients with large-volume stage II, III, and IV disease should include multiagent systemic chemotherapy. Involved field radiotherapy is recommended for these patients following the chemotherapy, especially in patients with residual masses larger than a few centimeters. Although not used frequently in the United States, infradiaphragmatic radiotherapy is a viable treatment option for patients with clinical stage I testicular nonseminomas. Such therapy results in approximately an 85% to 90% relapse-free survival rate, with an ultimate survival rate (including salvage) approaching 100%. Initial therapy for patients with stage II or greater disease generally should include chemotherapy and/or surgery. Radiotherapy is often useful as post-chemotherapy consolidation, especially for unresectable masses. For extra-gonadal seminomas, radiotherapy is useful as definitive therapy for small-volume disease and as consolidative therapy (postchemotherapy) for more advanced disease.