Recent studies suggest that cyclooxygenese-2 (COX-2) enzyme activation may play a role inhepatocarcinogenesis. However, the clinical significance of COX-2 expression in hepatocellular carcinoma (HCC)remains obscure. This study evaluated COX-2 expression in hepatitis B and hepatitis C virus related HCC andin HCC patients with an unknown etiology. Liver tissue samples of 31 patients with HCC (27 men and 4 women;age range, 48-75 years) were analyzed. COX-2 expression was evaluated by immunohistochemically in thetumor tissues. Patient data including age, sex, Child score, stage, grade of the tumor and survival were analyzed.Of these patients 19 were positive for hepatitis B virus (HBV), 6 were positive for hepatitis C virus (HCV) and 6patients were negative for all viral markers and other etiologic factors. COX-2 staining were evaluated in 2groups (group 1: COX-2 expression less than 25% (grades 1-2 COX-2 expression), and group 2: Cox-2 expression25% or more (grades 3-5 COX-2 expression). COX-2 expression was shown in all HCC samples with positive ornegative viral markers. No difference was found between degree of COX-2 expression and the etiology of HCC.COX-2 expression was not correlated with number of lesion or stage of the disease or grade of the tumor. COX-2 expression was not related with Child score of the patients. Median survival of all patients was 32 months.Median survival of patients did not differ according to patient’s viral marker status. No difference was observedin median survival of patients in group 1 and 2. As a result, COX-2 system seem to be shared part inhepatocarcinogenesis regardless factors that initiate the disease. Although COX-2 expression appears to beindependent of disease’s characteristics’, treatments that target this system appear to be feasible in themanagement of HCC.