The importance of apolipoprotein A-I (apoA-I) in atherosclerosis was established by testing in animal models, and its potential usefulness in humans has been confirmed in preliminary studies. ApoA-I is a large protein comprising 243 amino acids, which means that venous administration is necessary. In addition, manufacture of apoA-I is difficult and expensive. Research has, therefore, been directed towards finding smaller peptide mimetics that produce similar results to apoA-I, but that are easier to manufacture and administer. The earliest peptides mimicked some of the lipid-binding properties of apoA-I but did not prevent atherosclerosis in mice. A detailed study of the physical-chemical characteristics of these peptides led to the realization that the hydrophobic region of the peptide was critical in determining bioactivity. A potent peptide, 4F, which was synthesized wholly from D-amino acids, could be given orally. Use of 4F significantly improved the function of HDL in mice and monkeys. When 4F was administered in combination with a statin, lesion size and macrophage content were reduced in mice with atherosclerosis, and lesions regressed in older mice. Vasoreactivity and endothelial sloughing were also improved in other rodent studies. Early human clinical trials are now being carried out on 4F. Here, we review the studies on apoA-I mimetic peptides that have been carried out so far.