Contrary to high plasma levels of low-density lipoprotein cholesterol (LDL-C), closely linked with coronary heart disease (CHD), high-density lipoprotein cholesterol (HDL-C) play an antiatherogenic role, through the reverse cholesterol transport from peripheral cells to the liver. New data in the pathophysiology of a rare genetic dyslipidemia, the Tangier disease, characterized by very low HDL-C levels and premature CHD, have shed light on this complex mechanism. In this disease, cholesterol efflux from peripheral cells is dramatically reduced, and this has been recently shown to be caused by mutations in an ATP-binding cassette transporter, which normally stimulates cholesterol efflux. Reverse cholesterol transport is therefore greatly decreased. Epidemiological data have revealed that 15% to 30% of coronary patients have low HDL-C levels. However, this is often combined with high triglycerides levels, and this association is frequently found in diabetic patients, especially prone to CHD. HDL-C has been repeatedly shown to be an inverse predictor of CHD. This has been enhanced by recent interventional studies (Veterans Affairs HDL Intervention Study, Bezafibrate Infarction Prevention Study) which have provided strong evidence that pharmacological increase of HDL-C, in combination with decrease in triglycerides level, reduces incidence of CHD.