The aim of the study was to correlate the onset of epilepsy with the disease stage in children with brain tumors through treatment and follow-up in the oncologic department. The study sample consisted of a heterogenous group of 219 children who were aged 6 months to 11 years, manifested brain tumors, and had been treated and monitored in the Department of Pediatric Oncology of the Schneider Children's Medical Center of Israel since 1991. The overall rate of epilepsy was 14.6%, which rose to 38% in those with cortical tumors. Two major causes of epilepsy were evident: tumor-related and treatment-related. The first group could be further divided into epilepsy starting at or before diagnosis of brain tumor, epilepsy associated with tumor progression, and epilepsy starting at end-stage disease. The second group could be divided into epilepsy caused by radiation damage to the brain and epilepsy related to another postoperative state. The data emphasize the significance of striving for complete tumor resection and the potential damage from the use of radiotherapy to the brain. The authors suggest that a change in local neurotransmitter balance may be the mechanism underlying tumor-related epilepsy.