Concentration of magnesium in hair was measured by atomic absorption spectrophotometry in 3 groups of persons aged 48 to 79. All the participants of the study lived at least 10 years and none of them worked in industry or commerce. Their work place was in the distance less than 10 kilometers from their dwellings. The first group comprised inhabitants of the protective zone surrounding the Steel-Mill Huta im. Sendzimira, southern Poland, regarded as one of the biggest source of air, water and soil pollution. The second group constituted inhabitants of down-town Kraków (some 15 km from the steel-mill). The third group were the inhabitants of Tokarnia village with favourable microclimate. Though the concentration of magnesium in hair was similar to the one reported by other authors, it was shown that the concentration of this cation in hair was the smallest in the inhabitants of down-town Kraków and the highest in Tokarnia. The differences were statistically significant. It is postulated that magnesium hair concentration may be an easier, cheaper and less invasive indicator of body magnesium depletion.