Cardiovascular disease is a set of diseases affecting the heart and blood vessels. As with most chronic diseases whose incidence increases with age, it involves both inherited and environmental contributors and is therefore classified as a complex genetic disease. Most researchers believe that all major risk factors for cardiovascular disease have been identified. It is estimated that cigarette smoking, hypertension, abnormal serum cholesterol (low-density lipoprotein cholesterol or high-density lipoprotein cholesterol), obesity, lack of physical exercise, and diabetes account for 50 percent of the variability of risk in high-risk populations. The remaining risk is likely composed of a large number of yet-to-be identified minor risk factors or genetic influences that account for the development of disease in most individuals. Investigators who have attempted to estimate the overall contribution of genetics to the development of cardiovascular disease have proposed numbers ranging from 20 to 60 percent, based upon the analysis of...