100 unselected brains of patients dying at the ages of 55–64 years were examined for the presence of Alzheimer type changes. These changes were found in 25 brains. This number is lower than that in a comparable investigation from Japan, but it is clearly above the number found in selected nondemented patients from England. Although none of the patients had suffered from an easily recognizable presenile dementia, an important proportion of them had been noted for unusual psychology. The occurrence of Alzheimer type changes was not dependent on the diseases the patients had suffered fro