A class of lipoproteins, varying somewhat in their size (8-11 nm in diameter) and contents, that carry cholesterol from the body's tissues to the liver.

Because HDL can remove cholesterol from atheroma within arteries, and transport it back to the liver for excretion, they are seen as "good" cholesterol. When measuring cholesterol, any contained in HDL particles serves as protection to the body's cardiovascular health. (In contrast to "bad" LDL cholesterol.)