We examined the prevalence, phenomenology, and clinical correlates of delusions in a consecutive series of 103 patients with probable Alzheimer's disease (AD). Patients were examined with the Present State Exam and the Dementia-Psychosis Scale. Twenty-one patients (20%) met DSM-III-R criteria for a delusional disorder. The most frequent delusion type was paranoid (71%), followed by hypochondriacal (67%), the Capgras syndrome (29%), house misidentification (29%), and grandiose delusions (29%). Out of the 21 AD patients with delusions, 76% had three or more different types of delusions simultaneously. The frequency of delusions was not significantly associated with age, education, or age at dementia onset, and the type and severity of cognitive impairments was similar for AD patients with and without delusions. However, AD patients with delusions had significantly higher mania and anosognosia scores.