The effect of total hip replacement (McKee-Farrar and Brunswik prostheses) on selected activities of daily living and on the use of domestic aid in these activities was evaluated by interviewing 539 patients operated on. The mean age of the patients was 64.7 yr and the mean follow-up time 4.2 yr. After eliminating other diseases affecting mobility, a proper series of 294 patients was obtained. There was marked improvement in all activities. Walking ability was limited in 95% before and in 12% after the operation. The proportion of those unable to clean their homes decreased from 67-16%, to shop from 46-10%, to tie their shoes from 75-29%, to pull on stockings from 43-3% and to dress in other ways from 30-1%. The proportion of patients able to take care of themselves increased from 21-62%. The reliability of the interview was tested by comparing some objective observations with the information given by the patients. A correlation was observed between the ability to walk and shop and pull on stockings and the flexion range of the hip.