Using reasonable assumptions gathered from the published literature, we estimated that more than half of the decline in ischemic heart disease mortality between 1968 and 1976 was related to changes in lifestyle, specifically to reductions in serum cholesterol levels and cigarette smoking. In comparison, about 40% of the decline can be directly attributed to specific medical treatment of clinical ischemic heart disease and hypertension being the leading estimated contributors. Because many of these interventions have not yet been applied to their maximum potential, a continued decline in mortality rates might be anticipated in the coming decades. However, the relative costs of these medical interventions and lifestyle changes and the extent to which they interact with each other must be considered before an optimal national health strategy can be derived.