Age-adjusted overall ischemic heart disease mortality declined by 20.7% in the United States between 1968 and 1976. Declines were recorded in both sexes, in all age groups, and in three major race/ethnic groups. The decline cannot be explained by shifts in assignment of cause of death on death certificates. Available evidence suggests that improvements in diet with concomitant declines in serum cholesterol concentration, decreased cigarette smoking, improved hypertension control, and possibly increased leisure-time physical exercise explain a portion of the decline. Coronary care units have probably also contributed. Emergency medical services and coronary bypass surgery were not widely enough applied during this period to have contributed to the decline. Several strategies are suggested for further elucidating the relative contributions of various preventive and curative programs. Such information is urgently needed to foster optimum allocation of scarce resources between competing (and expensive) programs.