In a registry-based sample of 361 children with a brain tumor, those whose grandparents and great-grandparents had a history of any kind of tumor were younger at the time of presentation than were those who lacked this family history (p = 0.1). In post hoc analyses, the age difference was most apparent among children with cerebral tumors, and when family history was limited to brain tumors and to great-grandparents. These findings are in keeping with the hypothesis that a familial tumor diathesis contributes to an early age at onset of a brain tumor in some children.