The most important role of radiation therapy for carcinoma of the lung is its contribution to cure. Important technical advances in radiation therapy have been made that, along with advances in understanding the natural history of cancer of the lung, permit treatment with a higher expectation of cure than previously. Studies of fractionation have defined the doses required for control of intrathoracic tumors, and ancillary studies have better defined the treatment volumes necessary. Operable patients benefit from postoperative irradiation only when there is involvement of regional lymph nodes. In inoperable cases, the greatest survival benefit from radiation therapy is found among those who have a high performance status. Patients with adenocarcinoma and large cell carcinoma have a greater probability of long-term survival than those with squamous carcinoma. Investigations of altered fractionation may lead to improved results in radiation therapy for all histopathologic types of carcinoma of the lung.