This is a report of the initial (prevalence) screening for lung cancer in a population of 10.040 cigarette-smoking men 45 yr of age and older, recruited from metropolitan New York. All had posteroanterior and lateral chest roentgenograms, and approximately half the men, randomly chosen, also had sputum cytology (dual screen). Fifty-three confirmed lung cancers were found; 22 (40%) were AJCC Stage I, with 85% survival for 5 yr after resection, whereas only 2 of the remaining men with Stage II to III lung cancer lived longer than 3 yr. In the dual screen group, in which the 2 detection techniques could be compared, 6 Stage I lung cancers were detected by radiology alone, 7 by cytology alone, and only 1 by both techniques. All of the cases detected by cytology alone were squamous carcinomas, whereas two thirds of those detected by radiology alone were adenocarcinoma.