Seventeen clinico-pathological cases of leukoencephalopathy due to vascular diseases are reported. All of them had diffuse, often spotty demyelination sparing the U fibers, the corpus callosum, the internal capsule and the optic radiations. Microscopic examination of the white matter showed the association of the following lesions: oedema, swollen oligodendroglia, spongiosis, incomplete loss of myelin, astrocytic gliosis with Rosenthal's fibers, widening of the perivascular spaces with oedema fluid or hemosiderin laden macrophages, thickening and hyalinization of the blood vessels walls. Among those cases, 8 were consistent with Binswanger's subcortical encephalopathy (5 males, 3 females, mean age at death: 64 years, mean illness duration: 6, 7 years); all of them were hypertensive and had lacunae in the basal ganglia, hemispheric white matter and pons. Another case could be considered as a cortico-subcortical chronic hypertensive encephalopathy (77 y.o., female, illness duration: 4 years); she was hypertensive and had small cortical infarcts and perivascular bleedings, lobar and cerebellar hematomas, but no amyloid deposits in the blood vessels walls. Eight patients (5 males, 3 females mean age at death: 72 years, mean illness duration: 5, 4 years, 6 normotensive, 2 hypertensive) had diffuse meningocortical amyloid angiopathy with multiple small cortical infarcts, small cortical perivascular bleedings, slit haemorrhages and one or more lobar hematomas. Four of them had numerous senile plaques and neurofibrillary tangles. To our knowledge such a leukoencephalopathy in cerebral amyloid angiopathy has not been yet pointed out. It was present in 8 out of 12 cases of diffuse haemorrhagic form of cerebral amyloid angiopathy observed in the Charles Foix Laboratory of la Salpêtrière, during the last 10 years. A common mechanism with hypoperfusion of the distal white matter and alteration of the blood brain-barrier is suggested for this leukoencephalopathy.