Vanadium is an element whose role as a micronutrient and hypoglycaemic drug has yet to be fully clarified. The present study was undertaken to investigate the bioavailability and tissue distribution of vanadium and its interactions with magnesium in healthy and in magnesium-deficient rats, in order to determine its role as a micronutrient and antidiabetic agent. Four groups were used: control (456.4 mg magnesium and 0.06 mg vanadium/kg food); control treated with 1mg vanadium/day; magnesium-deficient (164.4 mg magnesium/kg food and 0.06 mg vanadium/kg food); and magnesium-deficient treated with 1 mg vanadium/day. The vanadium was supplied in the drinking water as bis(maltolato)oxovanadium (IV). The experiment had a duration of five weeks. We measured vanadium and magnesium in excreta, serum, skeletal muscle, kidney, liver, adipose tissue and femur. Fasting glucose, insulin and total antioxidant status (TAS) in serum were studied. The vanadium treatment applied to the control rats reduced the absorption, retention, serum level and femur content of magnesium. Magnesium deficiency increased the retention and serum level of vanadium, the content of vanadium in the kidney, liver and femur (organs where magnesium had been depleted), serum glycaemia and insulin, and reduced TAS. V treatment given to magnesium-deficient rats corrected magnesium content in muscle, kidney and liver and levels of serum glucose, insulin and TAS. In conclusion, our results show interactions between magnesium and vanadium in the digestive and renal systems. Treatment with vanadium to magnesiumdeficient rats corrected many of the alterations that had been generated by the magnesium deficiency.