Delirium on the day of admission to general internal medicine wards was studied in 400 consecutive patients aged 70 years and above regarding occurrence, associated factors, clinical profile, length of hospital stay, and mortality. The patients were assessed using the Organic Brain Syndrome Scale and the Mini-Mental State Examination, and delirium was diagnosed according to Diagnostic and Statistical Manual of Mental Disorders (4th ed) criteria. Delirium on the day of admission occurred in 31.3% of the patients and was independently associated with old age, fever on the day of admission (> or = 38 degrees C), treatment with neuroleptics, impaired vision, male sex, and previous stroke. Delirious patients had longer hospital stay (15.4 vs 9.5 days, P < .001), a higher mortality rate during hospitalization (11/125 vs 5/275, P < .001), and a higher 1-year mortality rate (45/125 vs 55/275, P = .001). Delirium is a common complication with often easily identified causes, and it has a serious impact on outcome for older medical patients.