Objective: To determine immunohistochemical expression of cyclooxygenase-1 (COX-1) in epithelial ovariancancer (EOC), and its association with clinical features and prognosis. Methods: EOC patients treated in BangkokMetropolitan Administration Medical College and Vajira Hospital during 1996-2003, and with availablepathological tissue sections, were identified. Immunohistochemical staining was accomplished with antibodiesto COX-1 and degree of expression was categorized into low and high for assessment of any. association withclinicopathological factors and survival. Results: One-hundred and seven patients were included in the study,with a median age of 50 years. Most had stage I and III disease. The most common histologic subtype was serouscarcinoma. Overall, we found COX-1 expression in 83.2 %. Non-mucinous lesions had significant higher levelsof expression than mucinous tumors, but there was no link expression with other clinicopathological factors orsurvival. Conclusions: EOCs showed highexpression of COX-1, especially with a non-mucinous histology, butthis appears to lack prognostic significance.