Coronary heart disease (CHD) is a complex disease that is affected by environmental as well as genetic factors. Research is ongoing that probes the relationship of human genetic variation to disease, potentially leading to better diagnosis and therapy. Variation in factors such as low-density lipoprotein cholesterol, apolipoprotein E, high-density lipoprotein cholesterol, apolipoprotein A-I/CIII/A-IV, lipoprotein lipase, cholesteryl ester transfer protein, lipoprotein (a), and homocysteine may affect CHD risk via genetic or environmental mechanisms or their interactions.