This synthesis of the literature on radiotherapy for lung cancer is based on 80 scientific articles, including 2 meta-analyses, 29 randomized studies, 19 prospective studies, and 21 retrospective studies. These studies involve 28172 patients. Basic treatment for limited-stage small cell lung cancer (SCLC), is chemotherapy. Addition of radiotherapy to the primary tumor and mediastinum reduces local recurrence, prolongs long-term survival, and is often indicated. Current, and future, studies can be expected to show successive improvements in results for SCLC by optimizing the combination of radiotherapy and chemotherapy. Should these treatments be given simultaneously or sequentially, and in which order? Which fractionation is best? Probably, no change in resource requirements for radiotherapy will be necessary, with the possible exception of changes in fractionation. Surgery constitutes primary treatment for nonsmall cell lung cancer (NSCLC) stages I and II. Radiotherapy may provide an alternative for patients who are inoperable for medical reasons. The value of radiotherapy following radical surgery for NSCLC remains to be shown. It is not indicated based on current knowledge. For NSCLC stage III, radiotherapy shrinks tumors and prolongs survival at 2 and 3 years. Whether it influences long-term survival after 5 years has not been shown. Considering the side effects of treatment, one must question whether limited improvements in survival motivate routine radiotherapy in these patients. Earlier attempts to add chemotherapy to radiotherapy to improve treatment results of NSCLC have not yielded convincing results. Several studies are currently on-going. Prophylactic cranial irradiation (PCI) greatly reduces the risk for brain metastases from SCLC. However, it has little influence on survival. Many treatment centers give PCI to SCLC patients who have achieved complete remission. This practice may be questioned since PCI is associated with serious complications. PCI is not indicated in patients with NSCLC. In SCLC, where the disease is extensive, only palliative radiotherapy is appropriate. Radiotherapy is an important treatment alternative in special palliative situations involving severe cough, severe bleeding, pain, pulmonary obstructions, and vena cava superior syndrome. In these situations, good results may be achieved with few fractions.