Pathological comparison between cases with Alzheimer-type dementia (ATD) and the non-demented cases with infarct showed that hippocampal atrophy in ATD could be caused mainly by degeneration of the stratum lacunosum-radiatum rather than neuronal loss in the pyramidal layer of the hippocampus, and that degeneration of the stratum lacunosum-radiatum could be secondary mainly to the entorhinal cortical degeneration.