Abstract: Objective ： To investigate the expressions of Cyclooxygenase-2 (COX-2) gene and protein in human gastric carcinoma and their relationship with clinical and pathological factors. Methods ：Reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry were performed to access the expression of COX -2 in malignant tissues, paired tissues adjacent to gastric cancers from 47 patients with gastric carcinoma. 11 specimen from normal gastric mucosa far from neoplasm also were detected at the same time. Results ： Strong expression of COX -2 mRNA was detected in 72.3%(34/47) of gastric carcinoma tissues(0.619±0.033), and increased expression in paired tissues adjacent to gastric cancers (0.175±0.084), but nearly no expression in normal tissues. There were significant differ-ence expression of COX -2 mRNA among gastric carcinoma tissues, paired tissues adjacent to gastric cancers and normal gastric mucosa. Immunohisto-chemistry analysis showed that COX-2 protein was expressed in 70.2% malignant tissues and 58.3% paired tissues adjacent to gastric cancers. The differ-ence is significant. There was no COX -2 protein expression in normal gastric mucosa. The strong expression of COX -2 has close correlation with lymphoid nodule metastasis and clinical stage of gastric carcinoma, but no noticeable relation to histology type or the depth of invasion. Conclusions ： The expression of COX-2 mRNA and protein elevated in human gastric carcinoma tissues, and the up-regulation of COX-2 has close relation with lymphoid nodule metastasis and clinical stage of gastric carcino-ma. Up-regulation of COX-2 may play an lmoortant role in progression and metastasis of human gastric carcinoma.