The purpose of this study was to determine the effect of dietary Mg deficiency (80 mg/kg versus control diet: 960 mg/kg) on blood pressure and mechanical properties of the rat common carotid artery. The internal diameter and intra-arterial pressure of carotid artery were measured continuously with an echo-tracking device. At 19 weeks, systolic, diastolic, and mean blood pressures were higher in Mg-deficient rats. Histological examination showed an increase in cross-sectional area, intima-media thickness, and media-to-lumen ratio in carotid artery of Mg-deficient rats. Mg deficiency did not modify the arterial distensibility-blood pressure curve. At mean blood pressure, arterial distensibility was significantly less in 19-week-old rats than in 5-week-old rats of both control and Mg-deficient groups. A significant interaction between age and Mg-deficient diet on arterial distensibility (P<0.04) indicates an accelerated age-dependent decreased arterial distensibility with Mg deficiency. At 19 weeks, the artery was stiffer in hypertensive Mg-deficient rats, as illustrated by a shift to higher levels of the incremental elastic modulus-stress curve. In conclusion, the increased blood pressure and the vascular morphological alterations observed in Mg-deficient rats may contribute to an accelerated alteration of the wall material, which in turn leads to a stiffening of the carotid artery.