The coronary vascular endothelium produces nitric oxide (NO) during the conversion of L-arginine to L-citrulline. Although NO is a potent vasodilator, at lower concentrations, it also has antineutrophil actions that reduce the inflammatorylike components of ischemia-reperfusion injury. The endothelium is damaged in the early minutes after reperfusion, ie, before neutrophils accumulate and before myocardial necrosis fully develops, and this suggests that endothelial injury is a springboard event in the postischemic inflammatory cascade. Studies of coronary artery occlusion and reperfusion suggest that early damage to the coronary endothelium impairs NO production, which, in turn, abrogates the endogenous antineutrophil effects of NO. However, this impaired endogenous NO-related cardioprotection can be restored either by providing specifically at the onset of reperfusion the precursor to NO (L-arginine) or by providing agents that donate NO. In studies, L-arginine or NO donors reduce infarct size in models of coronary occlusion and reperfusion. The mechanism or mechanisms of this cardioprotection involve preservation of endothelial function and inhibition of neutrophil accumulation in ischemic-reperfused tissue. The cardioprotective potential of NO offers a new therapeutic approach to the reduction of ischemia-reperfusion injury after coronary artery occlusion.