Two hundred cases of verified brain tumors occurring in patients under 15 years of age were studied in relation to possible etiologic, genetic, and environmental risk factors. They were compared with 100 age-matched patients harboring solid neoplasms outside the nervous system, as well as with 100 normal children. In our study, first-degree relatives of a brain tumor child did not show a higher incidence of either tumors or of epilepsy and strokes as compared with controls. First-born children (46%) with higher birth weights showed a greater tendency to present brain tumors. Dystocia (18.5%), previous miscarriages (18%), and dietary restrictions during pregnancy (3%) were also noted in this study and compared with data in the literature. No evidence of a role of maternal chickenpox and toxoplasmosis could be found. The pharmacological risk also seemed to be minimal. The mother's hormonal profile is deduced from the age at menarche and delivery, as well as from a tendency to miscarriages and complicated pregnancies. With regard to the immunologic aspect, it is worth noting that 15% of the mothers complained of allergies. Live polio vaccine and zoonosis might suggest a possible role of virus-related factors in the oncogenesis of brain tumors in children. Radiation-related risk is possibly present in less than 5% of cases. Parental occupation is not relevant in this series.