The hemodynamic and metabolic effects of dietary induced hypomagnesemia were studied in two groups of 2-month-old male spontaneously hypertensive rats (SHR). All rats were given distilled water to drink ad libitum and were followed for 2 months. However, control rats (n = 12) were given a regular rat diet to eat, whereas the experimental (hypomagnesemic; HM) rats (n = 12) were given a magnesium-free diet. Metabolic and hemodynamic studies were done at the end of the 2-month observation period in the awake state. HM rats had higher mean arterial pressure, total peripheral resistance, renal vascular resistance, heart rate, U<sub>Na</sub>V, U<sub>k</sub>V and serum Na, and lower hematocrit, renal blood flow, serum K and serum Mg than the controls. No differences were observed among the two groups of rats with respect to weight, fluid intake, urine volume, serum calcium, blood urea nitrogen, cardiac index and glomerular filtration rate. In addition, HM rats had widespread myocardial and renal tissue calcification in contrast to controls, which did not show any tissue calcification. We conclude: (1) dietary-induced hypomagnesemia aggravated the hypertension of SHR; (2) it caused widespread tissue calcification; (3) the adverse effects of hypomagnesemia on arterial pressure were possibly produced through calcium-mediated systemic vasoconstriction and increase in peripheral vascular resistance.