The Cohocton office of Tri-County Family Medicine has maintained an active screening program for breast cancer, colorectal cancer, and cervical cancer since 1974. This article reports a retrospective study of all patients with a diagnosis of cancer during the ten-year period from July 1974 to June 1984. Particular attention was paid to the relationship of screening to the diagnosis of these cancers. Sixty-nine cancers were diagnosed during the study period. Screening detected 7 of 11 breast cancers, 2 of 11 colorectal cancers, and 2 of 3 cervical cancers. In addition, all cases of respiratory cancer occurred in cigarette smokers and were therefore theoretically preventable. The data suggest that a large population of inactive, unscreened patients is a major obstacle to cancer prevention.