This study was conducted to evaluate the expression of p53 and c-erbB-2 using immuno-histochemical methods in 145 primary breast carcinomas and to correlate it with other histo-pathological prognostic factors. Invasive ductal carcinoma represented 129 of the cases. Expression of p53 protein and c-erbB-2 oncoprotein was present in 48% (62/129) and 30% (39/129) of invasive ductal carcinomas, respectively. The expression of p53 protein was stongly associated with a high score of degree of differentiation (p<0.05), nuclear pleomorphism (p<0.05), mitotic index (p<0.05), SBR grade (p<0.05) and MSBR grade (p<0.05), but it was not associated with patient's age, size of tumor or axillary node metastasis. The overexpression of c-erbB-2 C-erbB-2 oncoprotein was strongly associated with a high score of nuclear pleomorphism and a high SBR grade (p<0.05), but not associated with patient's age, size of tumor, axillary node metastasis, degree of differentiation, mitotic index or MSBR grade. An inverse relationship between the expression of p53 protein and estrogen receptor status was found, but the expression of c-erbB-2 was not associated with estrogen receptor status. It is concluded that p53 protein and c-erbB-2 oncoprotein are important prognostic factors in breast cancers, and that the aberrant expression of p53 protein is the most useful prognostic factor becausd of strong association of known histopathological prognostic factors and negative estrogen receptor status.