Aim To evaluate the distribution of induced cyclooxygenase (COX-2)expression in human coronary arteries with different atherosclerotic lesions. Methods 45 coronary arteries specimens from 15 autopsy cases were divided into 3 groups according to pathologic features of HE staining and AHA definition respectively,which were 3 healthy coronary arteries as control,22 fibrotic plaque or type Ⅴ lesion specimens (representing stable plaque),and 20 complicated plaque or type Ⅵ lesion specimens (representing unstable plaque). RT-PCR were performed for mRNA analysis,and immunohistochemical staining were used for location of protein. Results COX-2 was found in the areas of plaques but not in healthy or nonatherosclerotic vascular walls. COX-2 expression in complicated plaques was significantly higher than in fibrous plaques (COX-2 expression 147.0±1.1 vs 56.2±4.4,p<0.01). Conclusions These findings suggests that COX-2 might play a role in pathogenesis of atherosclerosis,and modulation of inflammatory process involved in plaque stability. Inhibition of COX-2 over-expression in plaque areas might be a potential approach to atherosclerosis treatment and plaque stabilization.