We report a unique pair of monozygotic twins with childhood epilepsy with occipital paroxysms who showed subtle cognitive deficits. The twin with a more severe epileptic disorder showed a more severe impairment of cognitive functioning. We suggest that epileptic focus may act as an element of disturbance in the development of primary functions and may give rise to a neuropsychological impairment proportionate to the severity of the epileptic activity.