Serum zinc concentrations were measured in 1416 Finns aged 15 years and above and belonging to 18 population groups living in various parts of the country. The mean serum zinc concentration was for men 12.7 mumol/l (82 microgram/100 ml) and for women 11.7 mumol/l (77 microgram/100 ml). Zinc levels varied with sex, age, length of fast, time of day and geographic area. It is noted that the incidence of coronary heart disease, the occurrence of a number of elements in soil and water, and the zinc level in human sera can in a statistical sence be linked to soil composition in Finland. Causal relationships, however, remain obscure.