The skeletal maturation of the upper limb distal segment was studied in 239 Spanish boys and girls between birth and 14 years of age. The atlas of Greulich and Pyle, offering standards of skeletal development of white North American children, was used as reference. The results obtained show firstly that in absolute terms, the ossification process is earlier in girls than in boys. This difference is maximum between 5 and 11 years of age. The boys show a delay of around 3 months with respect to their North American opposites. The girls, in contrast, show a better fit to the corresponding (female) standard of the atlas. In general, the highest agreement between bone age and chronologic age is for the ossification centers of the distal epiphysis of the ulna and radius and for those of the metacarpal bones. At the level of the carpus, individual analysis of the ossification centers shows that the capitate and hamate bones in the girls evolve most in accord with chronologic age. At the other extreme, and in both sexes, the ossification centers of the trapezium and trapezoid bones are statistically furthest from chronologic age.