The medical charts of 188 Alzheimer patients and a comparison group of 80 nondemented patients matched for age and sex were retrospectively reviewed for history of psychiatric morbidity. The Alzheimer patients were more likely to have had a psychiatric illness earlier in life (chi 2 = 8.5238, df = 1, P less than .001) with unipolar depression and paranoid disorder being the two most frequent psychiatric disorders. Possible explanations for these findings include underreporting, facility bias, functional psychiatric features as prodromal states of Alzheimer's disease, and vulnerability to psychiatric morbidity in those who go on to develop Alzheimer's disease. The likelihood of each of these explanations is discussed.