Single-view mammography was used for the screening of a total population of women living in a defined geographic region in Sweden; 37,640 women were invited and 31,074 participated. The average participation rate was 82.6%, and in the age group 40-69 years it was 91.7%. The rate of referrals from screening to clinical examination was 1.2%. Of 209 surgical biopsies performed, 130 primary mammary carcinomas were detected, 91% of which had no clinically detectable metastatic nodes. Because of the few false-positive cases, the low rate of benign biopsy specimens, the high rate of early detected carcinomas, and the low costs, screening by single-view mammography is considered a satisfactory method, provided the positioning of the oblique view is correct and the image quality is high.