A total of 183 consecutive patients undergoing biopsies for unilateral microcalcifications concentrated in one or more segments of the breast in the absence of any palpable findings were analyzed to characterize their risk of cancer. Biopsy findings were benign in 86 patients (47%) and malignant in 97 (53%). Of the clinical and mammographic characteristics evaluated, an increasing number of linear microcalcifications, either without a dominant density (p = 0.014) or with a dominant density (p = 0.019) and the presence of heterogeneous microcalcifications (p = 0.055), were associated with a significantly increased risk of malignancy. Conversely a fibronodular parenchymal pattern (p = 0.008) was associated with a significantly decreased risk of malignancy. A high-risk group was identified, 95% (40/42) of whom had malignant biopsy findings, whose mammograms had more than 10 linear microcalcifications not associated with a dominant density (16/17) or at least one linear microcalcification associated with a dominant density (24/25). Conversely a low-risk group for cancer was identified, 88% (28/32) of whom had benign biopsy findings, whose mammograms had exclusively punctate microcalcifications within a fibronodular parenchymal milieu (26/30) or demonstrated some change in the configuration of the microcalcifications on the various mammographic views (10/10). For the remaining 109 patients there was an almost equal division between malignant and benign diagnoses (49% vs 51%).