The aim of this study was to determine whether oral supplementation of melatonin (M), a known antioxidant, free radical scavenger and metal chelator, influences lead (Pb), calcium (Ca) and magnesium (Mg) distribution in the blood, bones and teeth of rats exposed chronically to lead. The studies were carried out on male Wistar rats which, from their birth until reaching sexual maturity (for 3 months), drank water containing 1% lead (II) acetate and/or received melatonin in feed (1mg/ kg body wt.) over a 3-month period. Concentrations of Pb, Ca and Mg were analyzed by atomic absorption spectrometry (AA S). Exposure to Pb and Pb plus M resulted in a significant increase in the Pb concentration in the whole blood (but below the threshold level) and bones in both groups. In rats chronically exposed to lead during their fast development (from birth until reaching sexual maturity), melatonin supplementation did not cause a significant decrease in Pb concentration in whole blood and bones. No changes were observed in blood plasma Ca and Mg concentrations in rats exposed to lead and treated with melatonin. However, their bones were observed to have a lower Ca concentration and higher Mg concentration, and their teeth higher Ca and Mg concentrations.