To study the entire population of Olmsted County, Minnesota, including all age categories, to examine the secular trends in coronary heart disease (CHD) mortality, myocardial infarction (MI) incidence, and natural history, including MI severity, case fatality and post-MI morbidity. Also, to examine the time trends in the prevalence of CHD at post-mortem because of the uniquely high autopsy rate in Olmsted County.