It is important to predict the prognosis of patient with cancer. Well known parameters predicting the prognosis are staged and degree of differentiation. Recently, the prognostic and diagnostic significance of silver-stained nucleolar organizer regions(Ag-NORs) and flow cytometric DNA analysis are introduced. This study aims to detect the diagnostic significance of Ag-NORs in breast lesions, and to correlate the number of Ag-NORs and cellular ploidies in breast carcinoma. In addition, the existence of heterogeneity according to the sample in the same patient is studied Sixty six paraffin blocks(two primary lesions and the two metastatic lymph nodes in 13 patients, and one primary lesion and one metastatic lymph node I 10 patients) of breast carcinoma, 30 paraffin blocks of fibroadenoma and 23 paraffin blocks of normal breast are studied. The numbe of Ag-NORs increase from normal breast(mean 1.45) through fibroadenoma(mean 1.60) to carcinoma(mean 2.43). It was significantly different between each lsions(P<0.0005). The number of Ag-NORs increased in the aneuploidy carcinoma than that in the euploidy one(P<0.05). But, there was difference between the number of Ag-NORs and DNA index according to the sample area in the same patient with carcinoma. In conclusion, the number of Ag-NORs is diagnostically significant in breast lesions and is correlated with cellular ploidies in breast carcinoma. In addition, Ag-NORs and cellular ploidies are heterogenous in the same patient.