To investigate the molecular mechanisms of laminar shear stress on the inhibition of apoptosis in endothelial cells, human umbilical vein endothelial cells (HUVECs) were starved in medium containing 2% fetal bovine serum (FBS) and treated with 15 dyne/cm2 shear stress. We confirmed that 15 dyne/cm2 shear stress inhibited the expression of Omi/HtrA2 at the mRNA and protein levels in cultured HUVECs. Furthermore, the release of Omi/HtrA2 from the mitochondria was induced by removal of basic fibroblast growth factor and decrease of FBS in the medium, while shear stress inhibited its release under the same conditions. These results suggest that downregulation of Omi/HtrA2 may contribute to the potent anti-atherosclerotic effect of shear stress by preventing endothelial cells from entering apoptosis.