Report of a case of linear nevus sebaceous of Jadassohn with the classical syndrome: 1) the facial linear nevus; 2) focal convulsions and 3) mental retardation. Skin biopsy didn't show proliferation of the sebaceous glands showing to be an early case. Computarized tomography showed slight cortico-subcortical atrophies, in contrast with the intensity of the mental retardation and focal crisis. Convulsions were controlled by several drug associations.