The aim of this study was to evaluate the effects of aging on endothelium-dependent and endothelium-independent relaxation of rabbit thoracic aorta from New Zealand white rabbits aged 4–6 and 7–12 months. The contractile response to noradrenaline (NA) decreased with increasing age, but NA [EC<sub>50</sub>] did not vary significantly. Acetylcholine (Ach)-induced relaxation of aortic rings precontracted with NA [EC<sub>50</sub>] did not change significantly with increasing age. The relaxation induced by ATP of aortic rings, precontracted with NA [EC<sub>50</sub>], was signficantly greater in young than in adult rabbits. This difference between young and adult animals became more evident in aortic rings deprived of endothelium: in adult animals, the ATP-induced relaxation of aortic rings with endothelium was significantly greater than in the rings without endothelium. The endothelium-independent relaxation by sodium nitrite (NaNO<sub>2</sub>) at lower concentrations was significantly greater in young than in adult rabbit aortic rings precontracted with NA [EC<sub>50</sub>]. Concluding, the age-induced changes in vascular response in male New Zealand white rabbits are related to an impaired mechanism at smooth muscle level.