The endothelium participates in the control of coronary vascular tone and growth through the release of vasodilating and growth-inhibiting factors such as nitric oxide (NO) and C-type natriuretic peptide (CNP), and vasoconstricting and growth-promoting substances such as endothelin-1 (ET-1). Abnormalities in NO and/or CNP generation or actions have been demonstrated in various cardiovascular pathophysiological states, specifically atherosclerosis, congestive heart failure, hypertension and hypercholesterolaemia. Moreover, an increase in plasma ET-1 levels has also been reported in these disease states. When these observations are considered together, these states may be characterised by an attenuated release or action of NO and/or CNP, together with an augmented release of ET-1. Thus, an imbalance between these opposing factors may contribute to the alteration in vascular tone and the vascular remodelling characteristics of cardiovascular disease. The following article summarises the present knowledge of endothelial control of the coronary circulation and derangements associated with coronary endothelial dysfunction.