Purpose: To evaluate morphologic characteristics of the clustered microcalcifications in benign lesions and tocompare with that of malignant lesions. Materials and Methods: We retrospectively reviewed 33 patients withclustered microcalcifications( five calcifications in number per square centimeter)on mammography. We analyzedmammographic findings with regard to shape, size, number/cm2, irregularity of size and shape, presence of centrallucency,and accompanied mass density. Results: Of 12 benign lesions, the most frequent shape was dot or round form(4/12, 33.3%) followed by ring form (3/12, 25%). The size were smaller than 0.5mm in 5 patients (41.7%), 0.5-1mmin one and more than 1mm in 6 patients(50%). The number of calcifications per square centimeter were five to tenin 41.7%, more than ten in 58.3%. Of all 21 malignant lesions, the most frequent shape was branching form (8/21,38.1%). The sizes of calcification were less than 0.5 mm in 76.1%(16/21). Central lucency within the calcificationwas seen only in benign lesions (3/14, 21%). Irregularity in size and shape of calcifictions was noted in bothbenign and malignant lesions. Accompanied parenchymal mass density was more commonly associated with malignantlesions(80.9%) than benign lesions(58.3%). Conclusions: Our results suggest that benign cluteredmicrocalcifications on mammography could be differentiated from malignant calcifications with the criteria oflarger size, central lucency and infrequent accompanied mass.