LDL is heterogeneous (Krauss and Burke, 1982) and can be separated on density gradient ultracentifugation into subclasses that vary in size, density and lipid content. In healthy subjects the most abundant LDL subclass is LDL-II. Women have proportionately more of the larger, less dense LDL-I particles than men. Conversely, men have proportionately more of the smaller, denser particles give rise to pattern B and larger, less dense particles to pattern A. It is clear from the work of Austin and Krauss and others that LDL pattern B is strongly related to CHD risk (Austin et al., 1988).