In five autopsied brains with senile dementia of Alzheimer type, the intrahippocampal routes of the perforant and alvear pathways were demonstrated by assessment of the distribution of isomorphic gliosis. Our results suggest that the perforant pathway goes along the stratum lacunosum-moleculare of the hippocampus proper to end in the dentate gyrus after perforating the prosubiculum but does not traverse the hippocampal sulcus, and that the alvear pathway enters into the stratum oriens of the hippocampus proper and the alveus from the white matter ventral to the subiculum.