We report the waking and sleeping polygraphic and evoked potential data recorded during the follow-up of a child with chronic progressive epilepsia partialis continua of childhood (Bancaud's type II). The findings that emerged from these investigations coupled with the clinical pattern enabled us to delineate the course of this rare condition and provided clues for a tentative interpretation of the pathogenesis of the repetitive myoclonic jerks typical of epilepsia partialis continua, on which there is as yet no consensus. In our case involvement of cortico-subcortical systems seems probable.