All patients with OA or RA entering an orthopaedic waiting list for total hip or knee replacement surgery over a period of 2.5 yr were prospectively assessed for overall pain (Visual Analogue Scale) and disability (Health Assessment Questionnaire) prior to and following their operation at annual intervals for up to 5 yr. A total of 293 patients had 335 operations (OA, hip 164; OA, knee 76; RA, hip 41; RA, knee 54). A few patients (14) showed a deterioration in pain and function 1 yr after surgery, but the remainder showed improvements which took 1 yr or more to reach maximum and were maintained for at least 3 yr. Although greater for OA hip patients, improvements occurred and were maintained in all groups, in spite of the polyarticular nature of RA.