Résumé : Objective: To assess magnesium enteral absorption from a magnesium-rich mineral water. Design: Experimental study. Setting: Department of Nuclear Medicine, Brugmann Hospital, Brussels, Belgium. Subjects: Ten healthy male volunteers in the age range 25-42y. Intervention: Each subject completed two sessions in a random order. At one session, they received an oral load of 300 ml of water (containing 1.2 mmol Mg), traced with 28Mg, and at the other session they received an intravenous injection of 28Mg, in order to take into account the metabolism of endogenous magnesium. The dietary consumption was further noted on a weekly diary. Results: The mean bioavailability was 59.1% (s.d. ± 13.6). Magnesium absorption and age were significantly inversely correlated (r= -0.68, P = 0.035). Conclusion: Magnesium-rich mineral water is a reliable source of magnesium. Our observation of decreased magnesium absorption with age deserves further investigations.