PURPOSE: To perform a medical audit of screening mammography for breast cancer and to determine the benefit of this procedure for the early detection of this condition. MATERIALS AND METHODS:We reviewed the results of 43,329 instances of mammography in 36,802 women [18-86 (mean, 46) years old] who underwent the procedure at our health promotion center between January 1995 and December 1998. After reviewing the mammographic reports, we selected ACR BI-RADS assessment cate-gories 0, 4, 5, and then reviewed the follow-up studies and the pathologic results thus obtained. By comparison with the total number of patients diagnosed with breast cancer during the same period, false negative cases were confirmed, and from these data a medical audit was performed. RESULTS: The percentage of women undergoing mammographic examination has increased in recent years (from 64.5% in 1995 to 97.4% in 1998), and cases of breast cancer among those aged 30 to 69 has tended to increase. A total of 1,879 cases were assessed as BI-RADS categories 0, 4, 5, and of these, 155 were recommended for biopsy or surgery. A confirmatory pathologic diagnosis was obtained in 106 cases, and in 43 of these, breast cancer was pathologically proven. The recall rate was 5.1%, and the cancer detection rate was 1.2/1000 population. Positive predictive value 1(PPV1) was found in 2.3% of cases, PPV2 in 27.7%, and PPV3 in 40.6%. The most common mammographic finding was microcalcification (40.5%), and a pathological finding of invasive ductal carcinoma was found in 66.7% of cases. Patients diagnosed with breast cancer totalled 47 (four cases were false negative); the estimated sensitivity was 91.5%, with a specificity of 95.0%. The percentage of minimal cancers found was 48.8, while that of axillary node-positive invasive cancers was 33.3. The total rate of axillary nodal metastasis was 22.0%, and the rate of stages 0 and I was 73.2%. CONCLUSION: When appropriate interpretation and follow-up monitoring of screening mammography is per-formed, the procedure is effective for the early detection of breast cancer.