Data on disease severity, co-morbidity, and process of care were obtained from the medical records of 356 patients without rheumatoid arthritis undergoing a first unilateral total hip replacement at four teaching hospitals in California and Massachusetts. Sociodemographic characteristics, functional status prior and subsequent to hospitalization, and improvement in health status were measured with a patient questionnaire 12 months after discharge. Completed questionnaires were received from 284 patients, a reponse rate of 79.8%. The questionnaire was acceptable to patients, reliable, and had good construct validity. The data indicate substantial benefits from hip arthroplasty. As expected, pre-surgical functioning was a strong predictor of outcomes 1 year after surgery. Controlling for pre-surgical functioning, age was not related to outcomes.