Alzheimer's disease involves cognitive and noncognitive manifestations including varying degrees of depression. The depressive syndromes of Alzheimer's patients are similar to those of nondemented patients and frequently are identified by patients themselves and their relatives. There is evidence that the depression of Alzheimer's disease is caused by familial and neurobiologic factors. The clinical importance in identifying depression in Alzheimer's disease lies in its responsiveness to antidepressant treatments.