Dementia is a social problem in Japan, as it is in other countries. Recently, there has been an increase in the number of patients with Alzheimer-type dementia (ATD) in the population. We analyzed 239 cases of patients autopsied at Fukushimura Hospital over a 10-year period. Clinicopathologically, 66% of these cases (158 cases) presented with dementia symptoms. The predominant form of illness was ATD. We found dementia with Lewy bodies (DLB) to be as frequent as vascular dementia (VD). Although the numbers were small, limbic neurofibrillary tangle dementia (LNTD) and Pick's disease (PiD) followed a clinical course typical of these diseases. On the other hand, senile dementia of the Alzheimer's type (SDAT) and the common form of neocortical type DLB (diffuse Lewy body disease; DLBD) were difficult to distinguish from each other. We attempted to uncover differences between these dementias in terms of how they affect male and female patients. The clinical course of the male patients with the common form of neocortical type DLB was more or less typical, while that of the female patients was not.