Depression is difficult to assess in Alzheimer disease (AD) and controversy surrounds the prevalence, etiology, and characteristics of mood alterations in patients with this disorder. We used a variety of standardized instruments to assess mood changes in 33 patients with AD. The frequency of depression ranged from 6 to 30%, depending on the diagnostic criteria employed. No relationship was found between patient depression and dementia severity, self-awareness of cognitive deficits (as measured by a memory self-rating scale), or mood of the caregiver. Delusional patients had higher scores on mood rating scales than nondelusional patients. The results suggest that depression in AD is not severe and is unrelated to patient self-awareness of illness. We hypothesize that the cholinergic deficit of AD may ameliorate depressive symptoms.