Reverse cholesterol transport is a complex process, which transfers cholesterol from peripheral cells to the liver for subsequent elimination as bile acids and neutral steroids. Although apo A-I in high density lipoproteins (HDL) is believed to have a crucial role in this process, clinical conditions with very low HDL cholesterol levels appear to maintain normal cholesterol excretion. On the other hand, infusion of 'artificial HDL' in the form of recombinant proapo A-I (4 g) liposome complexes results in increased fecal steroid excretion, corresponding to a removal of approximately 0.5 g cholesterol daily for up to 9 days. This occurs without evidence of increased cholesterol synthesis, and could not be reproduced by infusion of liposomes only. These data indicate that stimulation of reverse cholesterol transport may be induced by infusion of 'artificial HDL' in humans, and that a more detailed knowledge of this process may be useful in the treatment of atherosclerosis.