cases of numerous diffuse plaques in the neocortex but without severe senile changes in the hippocampus using modified bielschowsky method we studied neuropathologically 159 aged subjects autopsied during the period from 1976 to 1988 of which we found 19 cases average age at death 826 ys with numerous diffuse plaques in the frontal and temporal neocortex and no severe senile changes in h1h3 of ammons horn dp group amyloid angiopathy had been excluded and one case was excluded because of considerable cerebrovascular lesions the dp group was divided into 8 demented average age at death 860 ys and 10 nondemented patients average age at death 797 ys we compared the number type and ratio of types of senile plaques in the frontal cortex temporal cortex and putamen of the demented and nondemented groups and obtained the following results 1 eight 14 of the 59 nondemented and 8 40 of the 20 demented cases in which no severe senile changes in the neocortex and hippocampus had been detected by bodian stain showed numerous diffuse plaques in the neocortex when the modified bielschowsky method was used 2 the ratio of classic and primitive plaques to diffuse plaques in the frontal cortex was the same in both groups but the nondemented group had exclusively diffuse plaques in the temporal cortex 3 in the putamen 2 nondemented cases 20 and 6 demented cases 75 had exclusively diffuse plaques we considered that classic and primitive plaques are more closely related to dementia than are diffuse plaques in the temporal lobe in cases without severe senile changes in the hippocampus