Using a structured instrument, 325 elderly patients admitted to a general hospital for an acute medical problem were evaluated daily in order to detect symptoms of delirium. Patients were scored for 'hyperactive' or 'hypoactive' symptoms, and then the 125 patients with DSM-III delirium were rated as 'hyperactive type' (15%), 'hypoactive type' (19%), 'mixed type' (52%), or 'neither' (14%). There were no statistically significant differences between the groups with respect to age, sex, place of residence, or presence of dementia. These definitions of subtypes should be studied further.