Although the familial clustering of coronary heart disease has been well documented, it is unclear as to whether the familial clustering can be explained by shared environmental factors by members of a family or by clustering of risk factors having a genetic component such as blood pressure, familial hyperlipidemia and/or diabetes. Studies indicate that a family history of coronary disease may be an independent risk factor. Major histocompatibility complex genetic markers to identify individuals at risk within a family may be useful. In 1985 when the study began, there was a paucity of data dealing with the interrelationship of family history, genetic markers, immunological markers, and traditional risk factors.