Low HDL cholesterol is an important predictor of cardiovascular risk. Considerable effort has been undertaken to improve the predictive value of HDL cholesterol by the quantification of HDL subclasses. Controversy still exists as to whether quantification of apolipoprotein A-I, selective precipitation of HDL2, or differential immunoassays of apolipoprotein A-I-containing particles improve the diagnostic value of HDL cholesterol. Some quantitatively minor subclasses of HDL, namely pre-beta-1-lipoprotein(AI) and gamma-lipoproteinE, contribute significantly to the release of cellular cholesterol into the plasma compartment, and possibly to the antiatherogenic role of HDL. These particles can only be separated from the bulk of HDL by laborious electrophoretic techniques that, although provide important insights into the physiology of reverse cholesterol transport, are not suitable for clinical laboratories. Thus, to date, clinicians are not recommended to extend the measurement of HDL cholesterol to include the determination of HDL subclasses.