High density lipoproteins (HDLs) play a critical role in cholesterol metabolism and their plasma concentrations are inversely correlated with risk for atherosclerosis. The SR-BI (Scavenger Receptor BI) protein binds HDLs and mediates selective uptake of HDL cholesteryl ester. SR-BI binds HDL with high affinity, is expressed primarily in liver and nonplacental steroidgenic tissues, and mediates selective cholesterol uptake by a distinct mechanism. In mice, it seems that SR-BI plays a key rol