46 children, aged 2-6 years, with decreased magnesium concentrations in hair, were studied. Magnesium supplementation consisted of Asmag preparation for 3 months and multivitamin Multi-tabs preparation (containing magnesium, but without calcium) for the following 4 months. Control studies were performed again after 7 months of treatment, i.e. 12 months after the initial measurements (the same season of the year--early spring). The results proved increases of both magnesium (from 7.74 microg/g dry mass to 11.03 microg/g dry mass) and calcium (from 159.82 mg/g dry mass to 191.60 mg/g dry mass) concentrations in hair. Increased magnesium concentrations were observed in 40 studied children (86.95 per cent). Post supplementation magnesium deficiency was found in 22 children (47.83 per cent), and four children (8.70 per cent) showed further worsening of hypomagnesemia. Increased calcium concentrations were found in 42 children (91.30 per cent), while decreased Ca levels were found in 4 children (8.70 percent). The achieved results indicate a positive influence of that form of compensation of magnesium deficiency, and suggest the need of individual selection of doses and period of Mg supplementation. The initial level of hypomagnesemia, presence of factors that might inhibit intestinal absorption, accompanying diseases that might cause decrease in magnesium concentration and other factors that might influence the total body magnesium concentration should be taken into account while designing the supplementation therapy.