PURPOSE: To determine the value of mammography and ultrasonography in the detection of early breast cancer, and the usefulness of combining the two modalities for the diagnostic study of this condition. MATERIALS AND METHODS: The mammographic and ultrasonographic features of 47 female patients aged 23-68 (average, 46) years with pathologically proven early breast cancer were analyzed retrospectively. Mammography was performed in 46 patients and ultrasonography in 38, and 37 underwent both mammography and ultrasonography. Analysis of the mammographic and/or ultrasonographic features focused on mass, microcalcification, mass with microcalcification, multiple nodules, duct dilatation, and architectural distortion. RESULTS: Mammography revealed microcalcification in 29 (63%) patients, mass in 13 (28%) patients, mass with microcalcification in 8 (17%) patients, multiple nodules in 2 (4%) patients, architectural distortions in 1 (2%) patient, and negative finding in 9 (20%) patients. Ultrasonography revealed mass in 25 (66%) patients, microcalcifcation in 9 (24%) patients, mass with microcalcification in 8 (21%) patients, multiple nodules in 2 (5%) patients, duct dilatation in 3 (8%) patients, and negative finding in 7 (18%) patients. On combined study of mammography and ultrasonography of the 37 patients, mammography or ultrasonography revealed mass in 25 (68%) patients, microcalcification in 20 (54%) patients, multiple nodules in 2 (5%) patients, duct dilatation in 3 (8%) patients, and architectural distortion in 1 (3%) patient. In one (3%) patient among them, both mammography and ultrasonography revealed negative findings. The false negative rate of mammography, ultrasonography or both was 20%, 18%, and 3%, respectively, which was statistically significant difference (p < 0.05). CONCLUSION: Combined study of mammography and ultrasonography is the most useful as a diagnostic study for early breast cancer. So, ultrasonography seems to be the important additional method for detection of early breast cancer.