In 1974, screening trials indicated that both the sensitivity and specificity of single-view mammography are high. During the subsequent three years, 11 cases of breast carcinoma have been detected in the study population of 6,845 women aged 40 or older. The average incidence was three cases per year, compared to the expected rate of 8.9. The age-adjusted incidence rate in 1975, the year after screening, was 55.4 per 100,000, which is 40% of the expected rate of 140. In 1976 it was 75.9, or 54% of the expected rate of 141. These results support the view that single-view mammography is an efficient screening method, at least in the subject population described.