Background: Delirium or acute confusional state is defined as an acute disturbance of consciousness and attention. Its prevalence among hospitalized patients fluctuates between 25 and 60%. Aim: To assess the prevalence and features of delirium in an intermediate care unit. Patients and methods: All patients admitted to intermediate care unit during a period of two months were assessed and followed. Delirium was assessed daily during the stay in the unit, using the Inouye Confusion Assessment Method. Delirium was classified as hyperactive if the patient required pharmacological or physical restraining methods. Results: Sixty four patients, 32 female, aged 19 to 90 years old were assessed. Forty one percent had delirium. Of these, delirium started after admission in 46% and was hyperactive in 35%. Cognitive disturbances were ascertained by the health care team in 69% of patients with delirium. Age over 70 years old and a history of dementia were defined as predisposing factors for delirium. Serum albumin was > 3.5 g/dl in 14 of 18 patients with and in 11 of 27 patients without delirium (p=0.04). The most frequent risk factors were systemic infections, metabolic disturbances and intracranial lesions. Physical restraining and neuroleptics were the most commonly used measures to deal with hyperactive patients. Conclusions: The prevalence of delirium found in this study is similar to that reported elsewhere, except for the high proportion of patients whose delirium started after admission. (Rev Méd Chile 2000; 128: 75-79)