OBJECTIVE: To examine the prevalence, psychiatric and behavior symptoms, differing symptom profiles, and diurnal variations of delirium in older patients. DESIGN: A descriptive, point prevalence study with a cross-sectional design. SETTING: One ordinary county hospital (n = 148), three nursing homes (n = 202), five old people's homes (n = 196), and home medical care patients (n = 171) in parts of a hospital catchment area in Mid-Sweden. PARTICIPANTS: A total of 717 patients 75 years of age and older were observed and assessed for the prevalence of delirium. Women accounted for 66.4% of the studied population, and the mean age for both sexes was 83.7 years. MEASUREMENTS: All patients were examined using the OBS (Organic Brain Syndrome) scale, and delirium was diagnosed according to DSM-III-R. RESULTS: Delirium was diagnosed in 315 of 717 (43.9%) patients, and 135 of 315 (42.9%) of the delirious patients had dementia. Thirty-seven percent of the patients with delirium were delirious in the afternoon, evening, or at night, and 47% of the delirious patients had morning delirium. The delirious patients presented a wide variety of psychiatric symptoms. More than half the patients exhibiting anxiety, psychomotor slowing, depressed mood, and irritability. Nearly 26% were classified as having hypoactive, 22% as having hyperactive, and 42% as having mixed delirium, whereas 11% had neither hypo- nor hyperactive delirium. Seventy-seven percent were classified as having delirium with pronounced emotional and 43% with pronounced psychotic symptoms. CONCLUSIONS: This study shows that patients with delirium have very different clinical profiles. This might indicate a need for different treatment strategies for patients with different types of delirium.