The issue of whether seizures can arise in the cerebellum remains controversial. The authors present the first known case of focal subcortical epilepsy with secondary generalization thought to arise from a dysplastic lesion within the cerebellum. A newborn infant presented with daily episodes of left eye blinking, stereotyped extremity movements, postural arching, and intermittent altered consciousness lasting less than 1 minute. These episodes began on his 1st day of life and progressively increased in frequency to more than 100 events per day. Antiepileptic medications had no effect, and interictal and ictal scalp electroencephalography (EEG) recordings demonstrated bilateral electrical abnormalities. Magnetic resonance imaging revealed a mass in the left cerebellar hemisphere, and ictal and interictal single-photon emission computerized tomography revealed a focal perfusion abnormality in the region of the cerebellar mass. The patient subsequently underwent intraoperative EEG monitoring with cortical scalp electrodes and cerebellar depth electrodes. Intraoperative EEG recordings revealed focal seizure discharges that arose in the region of the cerebellar mass and influenced electrographic activity in both cerebral hemispheres. Resection of this mass and the left cerebellar hemisphere led to complete resolution of the patient's seizures and normalization of the scalp EEG readings. Neuropathological findings in this mass were consistent with ganglioglioma. A review of the literature on the cerebellar origins of epilepsy is included.