Two anatomo-clinical cases of a necrotic form of demyelinating disease are reported. The disease occurred in two women, had a late onset (patient were about 50 years old) and had a relapsing-remitting course during more than 10 years. The CSF displayed a high protein level over 125 mg/100 ml whereas the gamma-globulin level was normal. The anatomical study found symmetrical cavitations involving both hemispheres and optic tracts with clear-cut limits. Axons and myelin were both destroyed, only the vascular network being partially spared. At the lesion's border-line mononuclear cell infiltrates as well as some phagocytes with sudanophilic inclusions were found. The scarcity of the compound granular corpuscules suggest an old pathological process. A narrow zone of myelin-axonal dissociation was also observed. Astrocytic proliferations was unimportant. Blood vessels were normal. In one case plaques of multiple sclerosis were found in the spinal cord. Those two cases are unusual forms of a diffuse disseminated sclerosis: multiple sclerosis and Schilder's disease are considered as two anatomo-clinical variants of the same pathological process. The observed necrotic lesions are different from the acute necrotic forms of multiple sclerosis as the latter have rapidly developed. The long lasting course of the disease, over 10 years, allowed a complete resolution of the lesions explaining the cavitations. The late onset of the disease and the CSF high protein level are pointed out. The significant of the high protein level and normal gammaglobulin level in the CSF is discussed.