To determine the causes of the nationwide decline in deaths due to coronary heart disease, the Minnesota Heart Survey enumerated coronary deaths among persons 30 to 74 years old in Minneapolis-St. Paul. The survey also ascertained rates of hospitalization and case fatality during hospitalization for acute myocardial infarction. For deaths occurring between 1970 and 1978 that were due to coronary heart disease, the rates outside the hospital declined by 43 per cent in men and 40 per cent in women, and the rates in hospital emergency rooms increased by 311 per cent in men and 200 per cent in women. In both these years about two thirds of all such deaths occurred outside hospital wards. Between 1970 and 1980, hospitalization rates for acute infarction in persons 30 to 74 years old declined 8 per cent among men and 26 per cent among women, and case fatality in the hospital in persons 45 to 74 years old declined 29 per cent in men and 27 per cent in women. These changes are probably due to the combined influence of changes in risk factors in the population and improved care of patients with acute myocardial infarction before and during hospitalization.