Small cell lung cancer is an aggressive malignancy that is highly responsive to radiation therapy (RT), which has an important role in all stages of disease. For locally advanced, limited-stage disease, the standard of care is chemotherapy with concurrent radiation, which should be started early. The optimal radiation dose and field design remain to be determined. Randomized trials are currently being conducted to determine if dose intensification will improve outcomes, whereas consensus on elective nodal irradiation is evolving. Current studies are evaluating the potential benefit of consolidative thoracic RT in the management of patients with extensive-stage disease that has responded favorably to chemotherapy. Finally, prophylactic cranial irradiation improves survival in both limited- and extensive-stage disease that has responded to initial therapy.