Nine patients affected by schizencephaly were analyzed, and the epileptologic findings prospectively studied, to define the relations between the anatomic brain malformations and clinical outcome. The schizencephaly was diagnosed by means of magnetic resonance imaging (eight cases) or computed tomography (one case). The clinical histories of all the patients were analyzed, and a psychometric evaluation was made. The electroclinical features and course of epilepsy in the six patients with epilepsy were prospectively followed up for a period ranging from 3 to 14 years. The patients were divided into those who were unilaterally (six) and those bilaterally (three) affected. The former were characterized by mild neurologic deficits and late-onset epilepsy; their epileptologic features were consistent in terms of age of onset, seizure semiology, the absence of secondary generalization, and resistance to antiepileptic treatment. The patients with bilateral schizencephaly associated with other brain malformations were characterized by severe neurologic deficits but were only rarely affected by epilepsy, which was always completely controlled by antiepileptic treatment. Our data show that the extent of anatomic malformation is strictly related to the severity of motor and mental impairment but not to the presence or severity of epilepsy. The absence of prenatal risk factors for brain damage in our series, previously described familial cases of schizencephaly, and the recent report of mutations in homeobox gene EMX2 associated with cases of schizencephaly all indicate that genetic factors may play a key role in the pathogenesis of this brain malformation.