Since the beginning of the century, psychiatrists and neurologists have been arguing about the identity of presenile (Alzheimer's disease) and senile dementia. History reveals that the distinction was originally based on anecdotal clinical observations and that competition among universities was one of the underlying determinants. The personal opinion of Kraepelin played a major role. Given his widespread reputation and authority, he generated a dogma difficult to change. Reports based on large clinicopathologic series have shown that the pathologies of presenile and senile dementia are not qualitatively different. Although the controversy continues, many have come to regard Alzheimer's disease and senile dementia as part of the same spectrum of disease, independent of the age of onset.