A digital image processing system was used to study changes in orientation of the radiographic trabecular pattern of bone in children aged 4-14 years. The radiographs originated from a mixed-longitudinal growth study (The Nijmegen Growth Study), which comprised of three birth cohorts and which was carried out between 1971 and 1975. Of 3075 left hand-forearm radiographs of 426 children, the orientation of the trabecular pattern of the radius was analysed in twelve directions on a standard area of 10 x 10 millimetres. It was demonstrated that the trabecular pattern of the radius shows two predominant directions of orientation: along and perpendicular to the long axis of the radius. Spearman's Rank Correlations were calculated between direction of orientation and age of the children for the total population as well as for the cohorts separately, because the existence of cohorts-effects. The cohort of the youngest children showed more and higher significant correlations than the other cohorts, indicating that the trabecular pattern of young children is more subjected to changes. The results indicate that the prevalence of trabeculae orientated perpendicular to the long axis of the radius decreases. We speculate that this development reflects the effects of changes in mechanical loading in that direction during growth and development resulting in functional adaptation of the trabecular bone.