For ten years, a population of 6,136 male volunteers aged 45 years and over was screened every six months with 70-mm chest photofluorograms and with questionnaires regarding symptoms; 121 developed bronchogenic carcinoma. Only 8% of the men with cancer survived five years. Intervals between detection of the cancers and prior films read "negative" for cancer varied with volunteer cooperation. The five-year survival rate was 12% for 67 men whose tumors were detected within six months of a negative roentgenogram and 4% for 54 with intervals exceeding six months. In each of these two groups, some cases were found by the screen and some came to medical attention as a result of clinical illness. When cancer was detected by the screen, the survival curves were similar regardless of the interval between detection and the prior negative roentgenogram.