Objective: To investigate the clinical significance of COX-2 (Cyclooxygenase-2) expression in HCC ( Primary hepatocellular carcinoma) and clarify whether COX-2 is correlated with hypoxia-inducible factor-1α (HIF-1α) in the development of HCC.Methods: Tumor tissues were obtained from 53 patients with HCC. COX-2 and HIF-1α were determined by immunohistochemistry. All 53patients were regularly followed up and the data were collected prospectively. Results: Immunostaining showed the expression of COX-2( n = 33, 62.3 ％ ) and HIF-1α ( n = 36, 67.9 ％ ) in most tumor cells. The level of COX-2 was correlated with HIF-1α levels( r = 0.440,P ＜0.01 ). There were significant correlation between clinicopathological features and higher tumor cytosolic COX-2 level was in the presence of multiple tumors ( P = 0.01), venous invasion ( P = 0.03 ), advanced tumor stage ( P = 0.01), and well-different tumor grade (P = 0.03). High tumor cytosolic COX-2 level was correlated with patient's worse prognosis ( P = 0. 0085). Conclusion: Elevated tumor COX-2 level is correlated with elevated HIF-1α levels and invasiveness in HCC, suggesting COX-2 plays an important role in the progression of HCC, and may be an important therapeutic target in HCC.