Literature data oil the bioavailability of various Mg forms provide scarce information on the best Mg salt to be used in animal and human Supplementation. This Study aimed to investigate the bioavailability of different forms of Mg in rats using Mg stable isotopes. Eighty male Wistar rats aged 6 weeks were fed a semi-purified Mg-depleted diet for three weeks. The rats were then randomised into tell groups and received, for two more weeks, the same diet repleted with Mg (550 mg Mg/kg),is: oxide, chloride, sulphate, carbonate, acetate, pidolate, citrate, gluconate, lactate or aspatate. After 10 days of Mg-repleted diet, the rats received orally 1.8 mg of ail enriched Mg-26. Faeces and urine were then collected for 4 consecutive days. Isotope ratios in faeces and urine were determined. The Mg absorption values obtained varied from 50% to 67%. Organic Mg salts were slightly more available than inorganic Mg salts. Mg gluconate exhibited the highest. Mg bioavailability of the tell Mg salt Studied. Urinary Mg-26 excretion varied from 0.20 mg to 0.33 mg, and feeding with the organic pidolate, citrate, gluconate and aspartate salts resulted in higher urinary Mg-26 excretion than with inorganic salts. Ultimately, Mg-26 retention was higher in the rats receiving the organic salts such as gluconate, lactate and aspartate than in those receiving die inorganic salts. Taken together, these results indicate that Mg-26 is sufficiently bioavailable from the ten different. Mg salts Studied in the present, experiment, although Mg gluconate exhibited tile highest bioavailability under these experimental conditions.