High-density lipoproteins (HDLs) carry about 33% of the plasma cholesterol, while most of the remainder is carried by the low-density lipoprotein (LDL) fraction. The former appears to be associated with the efflux and redistribution of cholesterol present in non-hepatic tissues. In consequence, HDL is thought to play a prominent role in reverse cholesterol transport, which may be the basis for the negative association between plasma HDL levels and the prevalence of atherosclerosis within populations. Recent advances in the biochemistry of HDL and reverse cholesterol transport offer new hope of providing more powerful prognostic indices of the likelihood of premature coronary artery atherosclerosis in the individual. Currently, however, these new approaches are limited to research centres. An accurate HDL cholesterol assay, interpreted in the light of total cholesterol and particularly the atherogenic LDL fraction, is nevertheless capable of assisting in the recognition of the at-risk patient.