Hematocrit values are normally higher in natives living at high altitude than in natives living at sea level. Here, we have determined the hematocrit levels in relation to adrenal androgens in children living at altitudes of 150 m and 3400 m above sea level. The data demonstrate no association between serum adrenal androgens levels and hematocrit values. For all ages studied, hematocrit levels were higher in children at high altitude than in children at low altitude. Higher hematocrit values (> or = 54%) were observed in 15% of native boys at 3400 m. These data suggest that the higher hematocrit levels observed normally in children at high altitude are mainly related to altitude hypoxia and not to adrenal androgens.