In the present study we evaluated the prognostic significance and correlation between ploidy status, lymph node status, estrogen-progesterone receptor status and the expression of Erb-B2 and p53 protein in 77 primary breast carcinomas. Quantitation of DNA ploidy was determined on Feulgen-stained touch imprints with an image analyzer, whereas localization of the immunohistochemical reaction of Erb-B2 and p53 protein was evaluated in paraffin-embedded tumor specimens with microscopy. The DNA histogram was diploid in 17 cases, poly/tetraploid in 24 and aneuploid in 36. We observed no correlation between ploidy status and hormone receptor content or lymph node status. The expression of Erb-B2 protein was observed exclusively in the membrane and in the cytoplasm of neoplastic cells and was uniformly distributed. Overexpression was observed in 89.2% of cases. Aneuploid tumors intensively expressed the oncogene in 20.3% of cases. A statistically significant correlation was observed between lymph node metastasis and Erb-B2 overexpression. The expression of p53 protein was expressed as nuclear staining in 17.6% of the cases, with variable intensity, mainly in ductal histotypes. Among these, 62% were aneuploid. Lymph node status and steroid receptor status did not correlate significantly with p53. From these data we conclude that DNA ploidy and Erb-B2 and p53 expression correlate with cell proliferation and differentiation and therefore may identify breast carcinoma patients with more aggressive disease.