Epilepsy, together with mental retardation, represents a common manifestation of chromosomal aberrations. Specific electroencephalographic (EEG) and epileptic patterns have been described in several chromosomal disorders, such as Angelman's syndrome, Miller-Dieker syndrome, Wolf-Hirschhorn syndrome, and ring 20 syndrome. A peculiar electroclinical pattern has also been identified in trisomy 12p syndrome. We report three patients with a pericentric inversion of chromosome 12, with breakpoints localized to p11-q13 and affected by epilepsy or EEG anomalies. Two suffered from epilepsy, which, in the clinical course, was mainly characterized by complex partial seizures with a semiology related to the temporal lobe. In one patient, myoclonic absences, head drop, and massive jerky attacks were also present. In both patients, generalized 3 Hz bursts were registered, together with multifocal and focal paroxysmal activity, which were most prominent in the temporoparietal and temporal areas, respectively. In the other patient, who had no epilepsy, EEG showed bioccipital paroxysmal activity. In all patients, the clinical picture was characterized by the presence of moderate mental retardation and behavioral disorders. The incidence of epilepsy or EEG anomalies among patients with a pericentric inversion of chromosome 12 remains to be ascertained. However, the present study confirms that chromosome 12 anomalies can be associated with epilepsy. Although myoclonic absence-like episodes can occasionally be part of the epileptic phenotype, the electroclinical pattern in pericentric inversion of chromosome 12 seems to be more polymorphic when compared with that observed in trisomy 12p syndrome.