Silver-stained nucleolar organizer regions (AgNORs) in human breast carcinoma were studied using a computer-assisted system of image analysis. Standardized, automatic measurements of 7 morphometric parameters (area, perimeter, shape factor, bend energy, angle, and small and large diameters) performed on paraffin sections and cell imprint were compared and correlated with nuclear morphometry, histopathological grading, tumor growth fraction, (monoclonal Ki67-immunostaining), DNA nuclear content (stoechiometric Feulgen staining) and axillary lymph node invasion. The major findings were as follows: (i) variations in AgNORs and nuclear parameters were correlated, (ii) the ratio of AgNOR area/nuclear area was significantly different in low and high grade tumors, (iii) mean AgNOR parameter values increased significantly with the tumor growth fraction and tumor hyperploidy and were significantly higher in patients with axillary lymph node metastases and (iv) AgNOR evaluation was more accurate for cell preparations than for tissue sections.