Examined the frequency of delusions and hallucinations in patients with Alzheimer's disease (AD) and investigated factors associated with each or the combination of the two. Three hundred and forty-two community-residing patients (mean age 77.2 yrs) with probable AD were included in this cross-sectional, case-control study. Patients were assessed clinically for the presence of psychotic symptoms using the Mental Disorders-IV (DSM-IV) glossary definitions. The patients were also rated on standardized measures of cognitive impairment, depression, extrapyramidal symptoms, functional impairment and general health. Seventy-five (22%) AD patients had delusions only, 9 (3%) had hallucinations only and 30 (9%) had both delusions and hallucinations. Hallucinations were associated with less education, African-American race, more severe dementia, longer duration of illness, falls and use of anxiolytics. Delusions were associated with older age, depression, aggression, poor general health and use of antihypertensives. Patients with both delusions and hallucinations were similar to the patients with delusions only. This study confirms the high prevalence of psychotic symptoms in AD patients encountered in clinical practice and suggests that individual psychotic symptoms have different associations.