Two thousand consecutive patients aged 55 years and older admitted to a department of medicine in a large university hospital were examined for the presence of dementia. The occurrence of moderate and severe dementia was 9.1% for all age groups. It increased from 0.8% in the age group from 55 to 64 years to 31.2% in patients aged 85 years and older. Of the demented patients, 41.4% were delirious at admission, and 24.9% of all delirious patients were demented. Patients with vascular dementia constituted 72.4%, those with primary degenerative dementia 23.0%, and those with specific causes 4.6% of all demented patients. The mean hospitalization time for demented patients was significantly longer, and they needed significantly more daily nursing care, when compared with nondemented patients.