The purpose of the present study was to examine the importance of magnesium in endothelial function after arterial balloon injury. Male Wistar rats were fed normal, high or low concentrations of magnesium. Three weeks later the animals underwent endothelial injury of the thoracic aorta by a balloon catheter or a sham operation. Biochemical, histological and endothelial function analysis were performed 15 days after the surgical treatment. The animals fed a low magnesium diet presented the lowest level of serum magnesium and the highest ionized blood calcium levels. Histomorphometric analysis revealed no differences among groups neither regarding the magnitude of intimal thickening nor the recovery of endothelial coverage. However, when vasoreactivity responses were compared in the balloon-injured group, those animals fed a high magnesium diet had the better endothelium-dependent vascular relaxation. In conclusion, a higher magnesium level in the diet was beneficial to vessels that underwent endothelial injury by balloon catheter.