Surgical synovectomy in the treatment of rheumatoid arthritis has been performed for more than a 100 years, and yet the definite indication has not been made clear. Synovectomy has a convincing, but mostly time-limited effect on pain and articular hydrops, but the radiological progression continues almost undisturbed. Histological evaluation of the regenerating synovial membrane has now shown a tendency towards reversing to baseline within about a year. The difficulties in evaluating the operation are caused by the lack of comparable randomized studies performed on large populations, treated in a double-blind fashion and examined in cooperation between surgeon and rheumatologist.