In a 4-year longitudinal study, we evaluated factors related to the development of depressive symptoms in 410 persons with Alzheimer's disease. We measured depressive symptoms annually by using the 17-item Hamilton Rating Scale, which we completed by using structured interviews with family members. On the basis of informant ratings of premorbid personality, we associated neuroticism with a higher rate of depressive symptoms, particularly mood disturbances. We associated greater cognitive impairment with a small reduction in mood symptoms and a modest increase in somatic symptoms. Among demographic variables, somatic symptoms were more common in men and mood symptoms were inversely related to age. Depressive symptoms in Alzheimer's disease appear to follow a more predictable pattern of expression than previously described.