Atherosclerosis, the accumulation of cholesterol in the arteries resulting in heart attacks and strokes, is the leading cause of death in the USA and most other industrialized countries in the world. Plasma levels of high-density lipoprotein (HDL) cholesterol are invariably found to be inversely associated with the risk of atherosclerosis. This protective effect has classically been ascribed to HDL-mediated reverse cholesterol transport (RCT). In this process, nascent HDL in the circulation removes unesterified (free) cholesterol from peripheral cells, such as macrophages, through the transfer of cholesterol across the cell membrane by the ATP-binding cassette (ABCA1) transporter protein. The mature, spherical HDL particle, which contains these cholesterol esters in its core, then transfers the cholesterol to the liver through receptor-mediated processes. HDL cholesterol that is taken up by the liver is then excreted in the form of bile acids and cholesterol, completing the process of RCT. Because HDL-mediated RCT reduces serum cholesterol levels and is associated with a reduction in the risk of cardiovascular disease, increasing HDL is now being realized as a promising therapeutic end point.