A national survey of the patterns of care for carcinoma of the lung sponsored by the Commission on Cancer of the American College of Surgeons has documented continuing changes in epidemiology, treatment, and outcome. The project consisted of a long-term study of 15,219 patients whose diagnosis was made in 1981 and a short-term study of 19,074 patients whose diagnosis was made in 1986. The male/female incidence ratios have continued to decrease and the decrease has moved into the older age groups. Although the percentage of adenocarcinoma is increasing at the expense of squamous carcinoma, the latter is still the most prevalent histologic type. The accuracy of percutaneous needle biopsy and transbronchial biopsy of lung nodules reported from this group of 941 hospitals was high and equal to that reported by single institutions. The percentage of patients having a resection did not increase from 1981 to 1986, but for smaller lesions a move was apparent toward more lung-sparing resections. Little change has occurred in the use of adjuvant radiotherapy, particularly in stage III disease, where approximately 50% of the patients received postoperative irradiation. An improvement in the overall 5-year survival when compared with Surveillance, Epidemiology, and End Results data was noted. Whether this is a true improvement in survival or is the result of selection because of an unrecognized change in the pattern of care for patients with a carcinoma of the lung is unknown.