Cyclooxygenase is an enzyme that changes the immune response to malign cells and catalyzes prostaglandins that may have an impact on cell proliferation. The purpose of this study was to examine the relation between established clinicopathological parameters in breast carcinomas and COX-2 protein expression. COX-2, estrogen receptor (ER), progesterone receptor (PR) and c-erB-2 primary antibodies were assessed in the slides prepared from the paraffin blocks of 62 invasive ductal carcinoma cases. The relation between ER, PR, and c-erbB-2 positivity, histological grade, nuclear grade, lymphovascular invasion, tumor diameter, lymph node positivity, metastasis, and age were evaluated. The results were analyzed statistically. Cytoplasmic COX-2 expression was seen in 75.8% of all breast carcinomas. In both univariate and multivariate logistic regression analysis, there was a positive correlation between COX-2 expression and negative ER status, respectively (P=0.0173) (P=0.016). There was any statistically significant relation between PR positivity, c-erbB-2 positivity, histological grade, nuclear grade, lymphovascular invasion, tumor diameter, lymph node positivity, metastasis, and age (P≥0.05). Given that there was found a statistically significant relation between COX-2 expression and negative ER status, which is considered a poor prognostic parameter, suggests that COX-2 expression can have a place among the other prognostic parameters of breast carcinoma.