AbstractLung cancer is the leading cause of cancer deaths in both men and women in the United States. Treatment depends on the type and stage of lung cancer. For stage I and II cancer, surgery is usually the treatment of choice. Radiation therapy is used in patients who are considered poor risks for surgical resection. Intraoperative brachytherapy is an effective alternative to external irradiation in this group of patients. From 1958 to 1984, 55 patients with non‐small‐cell lung cancer were explored at Memorial Sloan Kettering Cancer Center and found to have surgical stage I or II tumors, which were considered to be unresectable mainly because of severe obstructive pulmonary disease precluding adequate resection. All these patients were treated with intraoperative brachytherapy at the time of the thoracotomy. Forty‐four percent of these patients received in addition external irradiation, mainly to the mediastinum. The overall 5‐year survival calculated by the Kaplan‐Meier Method was 32%, and the local disease‐free survival was 63%. Cox regression multivariant analysis demonstrated that there is a distinct subgroup with a better prognosis based on tumor site and patient's age—ie, patients who were younger than 58 years of age and had right