Several examples in recent literature show that the molecular principles governing intracellular cholesterol transport are starting to emerge. Two previously cloned proteins were discovered to play a role in sterol transport of steroidogenic cells: the scavenger receptor Bl as an HDL receptor and steroidogenic acute regulatory protein in the transport of cholesterol to mitochondria. Increasing evidence suggests the involvement of multidrug resistance proteins in sterol trafficking from the cell surface to the endoplasmic reticulum or across the plasma membrane. Specialized plasma membrane invaginations, caveolae, were implicated in cholesterol efflux, and the abundant caveolar protein, caveolin-1 which belongs to a newly discovered caveolin family of proteins, was shown to be a cholesterol-binding membrane protein.