Studies designed to elucidate the identity of the potent vasodilator autacoid endothelium-derived hyperpolarizing factor (EDHF) in the coronary vascular bed have highlighted a role for vascular cytochrome P450 (CYP) enzymes in cardiovascular homeostasis. Not only is there strong evidence suggesting that the putative coronary EDHF synthase is an endothelially expressed CYP epoxygenase, but CYP products such as epoxyeicosatrienoic acids and reactive oxygen species have been implicated in the regulation of intracellular signalling cascades and vascular cell proliferation. (Trends Cardiovasc Med 2000;10:166-170). (C) 2001, Elsevier Science Inc. All rights reserved.