AIM To study the effect of aspirin on TNFα induced adhesion of endothelial neutrophil and endothelial monocyte and its mechanism. METHODS Cell adhesion was measured by testing leukocyte myeloperoxidase activity; expression of adhesion molecules was measured by ELISA. RESULTS Aspirin(600 mg·L -1 , 900 mg·L -1 ) was shown to inhibit endothelial cells(EC) which were stimulated by TNFα for 6 h binding to neutrophil and monocyte. The rate of inhibition for endothelial neutrophil adhesion was 13 4% and 23 2% respectively; and that for endothelial monocyte adhesion was 14 9% and 24 3% respectively. If the time of stimulation was extended to 24 h, the effect of aspirin on endothelial monocyte adhesion was more potent(rate of inhibition: 20 0% and 38 9%), while it showed no effect on endothelial neutrophlil adhesion. This discrepancy was due to the selective inhibition of aspirin on adhesion molecules. CONCLUSION Aspirin inhibited TNFα stimulated endothelial neutrophil adhesion by suppressing the expressions of E selectin while inhibited endothelial monocyte adhesion by suppressing the expression of VCAM 1.