The use of hospital beds by elderly patients admitted to a Dublin teaching hospital was examined. Using objective pre-determined criteria, each day of hospital stay was evaluated in terms of whether the services provided or the patient's condition justified hospitalisation on a particular day. For days where the criteria were not met, the principal causative factor was identified. Of a total of 2,724 days of care reviewed, 792 (29.1%) were considered inappropriate. Female sex, age over 75, single status, residence with another adult or visits by the public health nurse prior to admission, and entitlement to free medical care were associated with inappropriate days of care. Self-referral, admissions to medical wards, for observation, social or multiple reasons and an admission diagnosis of cerebro-vascular disease were also associated with hospital misutilisation. The probability of a day being judged inappropriate became more likely with increasing lengths of stay. Physician and hospital factors accounted for almost one-half rehabilitation services only accounted for a quarter and lack of availability of alternative care facilities accounted for 39.5% of inappropriate beddays identified. Recommendations are made on how to improve appropriateness of care for elderly patients in acute hospitals.