The bioavailability of stabilized ferrous sulfate was studied by means of the prophylactic-preventive test in rats. For comparative purposes, ferrous sulfate was used as reference standard. The test was performed in male weaned rats during 3 weeks, which were randomized into three groups of ten animals each. A control group received a basal diet of low iron content while the other groups received the same diet added with iron at a dose of 15 mg/kg as FeSO4 7H2O and stabilized ferrous sulfate, respectively. Individual hemoglobin concentrations and weights were determined at the beginning and at the end of the study, and food intake was daily registered. Iron bioavailability (BioFe) of each source was calculated as the ratio between the amount of iron incorporated into hemoglobin during the treatment and the total iron intake per animal. A relative biological value was obtained as the ratio between the BioFe of stabilized ferrous sulfate and the reference standard given a value of 96%. Stabilized ferrous sulfate showed a high bioavailability, and when it is used to fortify dairy products as cheese and fluid milk in a dose of 15-20 mg of iron per kilogram, it behaved inertly in relation to the sensorial properties of the fortified food. These results suggest that this iron compound is a promising source to be use in food fortification.