Nitric oxide (NO) decreases cellular oxygen (O2) consumption by competitively inhibiting cytochrome c oxidase. Here, we show that endogenously released endothelial NO, either basal or stimulated, can modulate O2 consumption both throughout the thickness of conductance vessels and in the microcirculation. Furthermore, we have shown that such modulation regulates O2 distribution to the surrounding tissues. We have demonstrated these effects by measuring O2 consumption in blood vessels in a hypoxic chamber and O2 distribution in the microcirculation using the fluorescent oxygen-probe Ru(phen)3^2+. Removal of NO by physical or pharmacological means, or in eNOS^¯/¯ mice, abolishes this regulatory mechanism. Our results indicate that, in addition to its well-known effect on the regulation of vascular tone, endothelial NO plays a major role in facilitating the distribution of O2, an action which is crucial for the adaptation of tissues, including the vessel wall itself, to hypoxia. It is possible that changes in the distribution of O2 throughout the vessel wall may be implicated in the origin of vascular pathologies such as atherosclerosis.