Altered plasma lipid, lipoprotein, and apolipoprotein levels are associated with the occurrence of coronary heart disease, non-insulin dependent diabetes, and gallbladder disease. Although there are many other environmental and biological correlates, clinical, epidemiological, and experimental lines of evidence indicate that lipid metabolism has a central role in the development of coronary heart disease. Evidence pointing to the association between measures of lipid metabolism and other chronic diseases is no less compelling. Non-insulin dependent diabetes mellitus exhibits both the diagnostic abnormal carbohydrate utilization, and altered lipid metabolism. The hypothesis that abnormal lipid metabolism may be causally involved in gallbladder disease is suggested by the presence of cholesterol saturated bile several years prior to the onset of clinically definable gallstones.