The purpose of this symposium was to evaluate the hypothesis that the beneficial effects of training are the result of training-induced adaptations in the coronary circulation. The approach is to review, summarize, and evaluate data concerning the effects of exercise training on the coronary circulation. Results indicate that aerobic exercise training induces an increase in both blood flow capacity and capillary exchange capacity. These functional changes are the result of two major types of adaptive responses: structural vascular adaptation and altered control of vascular resistance. Structural vascular adaptation occurs in response to exercise training in at least two forms: increases in the cross-sectional area of the proximal coronary arteries, and angiogenesis. Training-induced changes in coronary vascular control have been shown to include altered responses of the coronary circulation and isolated coronary arteries to vasoactive substances, changes in endothelium-mediated vasoregulation, and alterations in the cellular-molecular control of intracellular free Ca2+ in both endothelial and vascular smooth muscle cells isolated from coronary arteries of exercise trained animals. The potential impact of these training-induced adaptations on the coronary collateral circulation and atherosclerotic coronary disease are discussed.