Insulinoma is a common cause of seizures due to recurrent hypoglycemic crises. Surgical treatment usually results in disappearance of such seizures. We describe a previously healthy 17 year-old girl who became epileptic after the onset of insulinoma with persistent seizures after surgical removal of the tumour. Insulinoma must be taken into account for differential diagnosis with convulsions of unknown origin, and even after metabolic normalization it may cause epilepsy.