The effect of total hip replacement on the health-related quality of life of patients who have osteoarthrosis was examined as part of a randomized, controlled trial comparing femoral head prostheses that were inserted with or without cement. One hundred and eighty-eight patients were followed for three months: 179 of them, for six months; 156, for one year; and ninety, for two years. The health-related quality of life was assessed with use of the Harris hip score, the Merle d'Aubigne hip score, the Sickness Impact Profile, the Western Ontario and McMaster University (WOMAC) Osteoarthritis Index, the McMaster--Toronto Arthritis (MACTAR) Patient Preference Disability Questionnaire, and the time trade-off technique as a measure of utility. Patients also took the six-minute-walk test. The mean age of the patients in the study was sixty-four years (range, forty to seventy-five years); ninety-seven patients (53 per cent) were men and ninety-four (50 per cent) had a prosthesis inserted with cement. Only three of 188 patients refused to return for quality-of-life assessments. There was significant improvement in all health-related quality-of-life measures and in the six-minute-walk test after the operation (p < 0.01 for all items, except for the work dimension of the Sickness Impact Profile at three months [p = 0.07]). Most of the improvement had occurred by three months postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)