PURPOSE: The purpose of this study was to perform a medical audit of the screening of mammographic results according to ACR BI-RADS Follow-Up and Outcome Monitoring and to evaluate the efficacy of screening mammography in the early detection of breast cancer. MATERIALS AND METHODS: We reviewed the results of 15,300 mammographic examinations of 13, 889 women aged 30 -75 years who underwent mammography at least once at the Severance Health Promotion Center between 1994 and 1998. Women with abnormal mammographic findings were recalled for additional study and those with dense breast composition (3, 4) underwent additional ultrasound. All results were categorized on the basis of the ACR BI-RADS final assessment scale, 1 -5. We reviewed the pathologic or follow-up results of all women in categories 4 and 5, and/or those in any category who took the films out of the health center. RESULTS: The recall rate was 13%. Biopsy or surgical Consultation was recommended for 92 women and biopsy was performed in 52. Pathology revealed 17 cancers and 35 benign lesions. Positive predictive value 2 was found in 18.5% of cases, and positive predictive value 3 in 33%. The cancer detection rate was 1.2/1,000, and sensitivity was 89.5%. Invasive cancers smaller than 1cm or in situ ductal cancers were found in eight of 17 cases (47%), while node-positive invasive cancers were found in nine of 14 cases (64%). Four of 17 mammo-graphically detected cancers were palpated by a surgeon. CONCLUSION: In asymptomatic women, screening mammography is an effective method for the detection of early breast cancer.