The Zlatibor district in Serbia has lower mortality rates of malignant and cardiovascular diseases (CVD) compared with other regions in Serbia. To better understand the influence of the geochemical environment, we collected and analyzed soil from various bedrocks and the grass growing on them. We also analyzed spring and stream waters, including large water supply accumulations, for major chemical elements and examined the serum of healthy adults in the large area of Zlatibor for selenium (Se) and magnesium (Mg). Our studies included villages, small towns, and the town of Uzice. Our results showed a variable Se content in the soil over different bedrocks. In general, soil in this area has a higher Se content than in other regions of Serbia. The Se content of the grass is influenced by bedrock and soil mineralogy, but mostly by soil pH and the date of collection. For example, in late summer, grass contains twice as much Se than in spring. Mg2+HCO3(-)-type waters occur in the ultramafic massif of Zlatibor in a concentration of 44 to 68 mgMg/L. The serum Se values were higher in the Zlatibor area than in other regions of Serbia (62.6 +/- 14.9 microgSe/L; n = 158). The serum Mg content (22.7 +/- 2.2 mg/L; n = 158) was in the uppermost part of the reference range. Taking into account their biological role, the Se and Mg levels in the human population in the Zlatibor area could influence the lower mortality rates of cancer and CVD in this region compared with other regions in Serbia.