Healthy men and women aged 19 to 80 years (n=122) and living without any restriction were studied to determine the age and sex dependence of plasma, erythrocyte and urine copper, zinc and magnesium concentrations and to establish correlations between these parameters. Subjects were divided into 3 groups according to age and in 6 subgroups according to sex: 1) 40 subjects (19 mean, 21 women) aged 19 to 39 years, 2) 37 subjects (20 men, 17 women) aged 40 to 59 years, and 3) 45 subjects (25 men, 20 women) aged 60 to 80 years. Plasma copper showed an age related increase, with higher concentrations in women of the first two groups. Plasma zinc and magnesium were significantly lower in the elderly. Erythrocyte zinc and magnesium increased with age while erythrocyte copper decreased in the oldest age group. Urinary excretion of copper and magnesium decereased with age. Urinary zinc excretion was significantly higher in the men of the middle-aged group. A strong negative correlation was present between plasma and erythrocyte copper and zinc in all groups, and a significant positive correlation was observed between plasma and erythrocyte magnesium and zinc in the two younger groups. Plasma zinc and magnesium were positively correlated up to 60 years. A positive correlation between urinary magnesium and copper concentrations was present only in the elderly. These findings suggest that age and sex are factors influencing trace element homeostasis and their interactions. These data may provide a reliable basis for the interpretation of trace mineral levels and interrelations in acute or chronic changes due to disease or drugs.