The records of 291 children treated over a 10-year period for intracranial tumor were examined, with particular attention to patients with seizures. Seizures occurred in 17% of the total group—in 25% of patients with supratentorial tumors and in 12% of those with infratentorial tumors. They were the initial symptoms in 15% of patients with supratentorial tumors and in 1% of those with infratentorial tumors. The average age at onset was 4.9 years in the supratentorial group and 4.8 years in the infratentorial group. The diagnosis of supratentorial tumors was delayed for an average of 2 years, whereas infratentorial tumors were diagnosed within an average time of 3 months of the initial seizure. Eight patients continued to have seizures for periods between 3 and 8 years before a tumor was suspected. The pattern of the initial seizure was of localizing value in 75% of patients with supratentorial tumors that involved the cerebral cortex and in 16% of patients with infratentorial tumors. In patients with seizures the electroencephalogram was of localizing value in 92% of tumors that involved the cerebral cortex, and abnormalities maximal in the occipital areas were compatible with the localization of 44% of infratentorial tumors. Spike, sharp wave, or spike and wave seizure discharges were present in 32% of patients with supratentorial tumors.