The results of arthroscopic synovectomy of the knee joints were reviewd in 23 joints of 21 patients hetween May 1992 and June 1996. The results were as follows: 1. Pain, tenderness, swelling, ROM of synovitis syrnpknns were much nsiproved postoperatively. 2. The degrees of articular cartilage damage were closely related to posto-perative functional recovery. 3. Preoperative and postoperative ESR changes were not ditferent signihcantly, 4. Recurrence rate was 17%, 4 cases. Of them, 2 cases were rheumatoid arthritis, 1 case was pigmented villonodular synovitis, I case was nonspecipic synovitis 5. Complicatior of arthrosc:opic synovectomy was nol found. We concluded that arthroscopic synovectoiny was very useful method of early diagnosis and treatment of synovial memhrane diseases.