Six children who received craniospinal irradiation for medulloblastoma when they were under 10 years of age developed learning disabilities. Four exhibited associated temporal lobe calcification on computerized tomography of the brain. The pathogenetic mechanisms of postirradiation cerebral calcification and learning disabilities in these children are discussed. We present the hypothesis that irradiation-induced vasculopathy results in hypoxia, most pronounced in the hippocampus. Hippocampal damage can manifest radiologically as calcifications and clinically as memory and learning disabilities.