Median daily iron absorption was determined in iron-replete males and females between 2 and 19 years of age from the upper and lower socioeconomic strata of the Venezuelan population. A comparison was made with iron absorption of well-nourished children, on the basis of hematological and anthropometric reference values from the U.S. The median absorption level, which was calculated from the increase in total body iron due to growth and the daily losses through exfoliation and menstruation, was also used to estimate the requirements of 95% of the population. When the requirements were expressed in terms of body weight, no significant difference in iron absorption was observed between the three Venezuelan and one U.S. groups, ranging from about 30 to 38 micrograms/kg/day in both sexes between 4 and 16 years of age. However, when the requirements were expressed without division by the weight factor, the requirements of the better nourished groups were somewhat higher than those of the Venezuelan lower socioeconomic population with, in addition, a threefold variation over the 5 to 16 year age range. These findings suggest that the total iron requirements of children at a certain age may be most adequately expressed in terms of the optimal body weight for that age.