In a study of 56 breast cancer patients (infiltrating ductal carcinoma) with a follow-up period of more than 5 years, bcl-2 and p53 oncoprotein were determined by immunohistochemistry. The aims of this study were two folds: (1) to determine whether bcl-2 and p53 are expressed in breast cancer and its possible role in cell transformation, on the light of the relationship to estrogen and progesterone receptors, and (2) to assess whether bcl-2 and p53 immunoreactivity is associated with important clinicopathological parameters and with patient survival, including estrogen and progesterone receptors. Twelve of 56 (21.4%) carcinoma were Bcl-2 positive, and seventeen (30.4%) were p53-positive. A positive relationship was seen between bcl-2 and estrogen receptor (ER), with 11 of 12 (91.7%) bcl-2 positive tumors being ER positive (0.05<p<0.1), but no significant relationship was seen between the bcl-2 and progesterone receptor (PR)(p>0.05). A strong negative relationship was observed between p53 and ER with seven of 17 (52.9%) p53 positive tumors being ER positive (p<0.05), and between p53 and PR with eight of 17 (47.1%) tumors being PR positive (p<0.05). Bcl-2 protein expression showed a significant relationship to low histologic grade of tumor (p<0.05), lower recurrence rate (0.05<p<0.l). The p53 protein expression showed a significant relationship to high histologic grade of tumor (P<0.05) and lymph node metastasis (0.05<p<0.l). Thus, an inverse relationship was found between bcl-2 and oncogene p53 (p=0.087). Tumor size (p=0.0001), progesterone receptor (p=0.0021), histologic grade (p=0.07) had a significant influence on survival. Bcl-2 immunoreaction was associated with longer overall survival of patients (0.05<p<0.1), but p53 immunoreaction was not to be associated with shorter overall survival of patients (p>0.l). In conclusion, the role of bcl-2 in breast cancer is presumed that bcl-2 may be an ER- regulated gene and loss of bcl-2 expression in breast cancer is associated with a range of molecular markers of poor prognosis and maybe define part of ER negative phenotype. The data presented herein may also have therapeutic implications that bcl-2 immunoreactivity of breast carcinoma can be a predictor of a therapeutic response to antiestrogenie therapy. The p53 expression may be also marker of aggressive carcinomas. But this prognostic power is likely to be weak and unlikely, therefore, to be of clinical significance.