The first report from the Framingham Study that demonstrated an inverse relationship between high-density lipoprotein cholesterol (HDL-C) and the incidence of coronary heart disease (CHD) was based on four years of surveillance. These participants, aged 49 to 82 years, have now been followed up for 12 years, and this report shows that the relationship between the fasting HDL-C level and subsequent incidence of CHD does not diminish appreciably with time. Since a second measurement of HDL-C is available eight years after the initial determination, the relationship of HDL-C measurements on the same subjects at two points in time is examined. This second HDL-C measurement is also used in a multivariate model that includes cigarette smoking, relative weight, alcohol consumption, casual blood glucose, total cholesterol, and blood pressure. It is concluded that even after these adjustments, nonfasting HDL-C and total cholesterol levels are related to development of CHD in both men and women aged 49 years and older. Study participants at the 80th percentile of HDL-C were found to have half the risk of CHD developing when compared with subjects at the 20th percentile of HDL-C.