The association of bilateral basal ganglia calcification subsequent to therapeutic irradiation of the cranial vault and brain has not been previously recorded. This report gives a description of such a relationship in 2 children, one of whom had a hypothalamic glioblastoma multiforme and the other histiocytosis of the skull. The calcification was detected roentgenographically 3 and 9 years following irradiation, at which time both children were 12 years of age. There was no disturbance of calcium or phosphorus metabolism in either child and no roentgenographic evidence of calcification of the basal ganglia prior to irradiation. The pathogenesis of the calcification is likely to be local tissue hypoxia resulting from radiation damage to the small vessels of the basal ganglia.