Sphingosine 1-phosphate (S1P) is concentrated in lipoprotein, especially high density lipoprotein (HDL), in plasma. We characterized the role of HDL-associated S1P in HDL-induced anti-atherogenic effects. HDL-associated S1P mediated HDL-induced stimulation of proliferation, migration and inhibition of apoptosis through S1P specific receptors S1P1 and/or S1P3 in endothelial cells. On the other hand, HDL-induced nitric oxide production and inhibition of adhesion molecule expression were mediated by two pathways, i.e, HDL-associated apoprotein A-I, A-II/SR-BI and S1P/S1P receptors in endothelial cells. Thus, in endothelial cells, HDL-associated S1P is a key player of HDL-induced anti-atherogenic effects.