To determine the diagnostic utility of the finding of naked, bipolar nuclei in fine needle aspirates of breast lesions. Aspirate smears from 150 cases of histologically proven benign (77) and malignant (73) breast lesions were evaluated for the presence of stripped, bipolar nuclei in the smear background as singlets as well as closely associated pairs. The presence of such pairs was a more specific indicator of benign entities (present in 70% of benign lesions vs. 1% of carcinomas) when compared to single, bare nuclei alone (present in 94% of benign lesions vs. 45% of carcinomas). Large numbers of such "benign pairs" also strongly favored the diagnosis of fibroadenoma within the benign subgroup. The presence of bipolar nuclear pairs is a valuable addition to the finding of singlets in the diagnosis of benign breast lesions and their subclassification.