Objective: To evaluate the expression of cyclooxygenase (COX)-2 in ovarian serous carcinomas (OSC) and its correlation with microvessel density (MVD), nm23 expression, clinicopathologic prognostic factors and survival. Methods: Specimens from 44 patients with OSC were evaluated by immunohistochemistry for COX-2 and nm23 expression. Tumor MVD was assessed with CD34 immunostaining. The survival data of the patients were found from data files. Results: 40 specimens (90.1%) showed positive COX-2 staining. Patients with high COX-2-expressed tumors had shorter overall survival, but it was not statistically significant. No correlation was found between COX-2 expression and clinicopathologic variables. There was no significant correlation between COX-2 and nm23 expression or MVD. Conclusions: COX-2 is frequently expressed in OSC. Although we could not confirm the prognostic significance of Cox-2 expression in the present cohort of OSC patients, the p value for overall Survival was just slightly greater than alpha, and this result can be referred as almost significant. We considered that the limited number of cases in Our study might affect the statistical analysis of our results. Further studies involving a larger number of patients are needed to clarify the prognostic significance of COX-2 expression in ovarian carcinomas.