Nine patients with rheumatoid arthritis (10 knees) with chronic knee synovitis unresponsive to medical therapy were entered into a prospective study of arthroscopic total synovectomy of the knee. Histopathological examination of the synovium revealed a proliferative synovitis in all knees. Patients were ambulatory and exhibited 90 degrees of knee flexion on the day after surgery and were discharged at 24 to 48 h postoperation. Mean joint tenderness and swelling improved from the preoperative level and was maintained for the initial 12 months of the study. Knee range of movement was improved in all patients (mean 21 degrees). Improvement of joint function in daily activities was also demonstrated, but patients with Grade IV articular cartilage damage failed to show significant improvement. Nine knees were followed for at least 24 months and 4 required repeat surgery. Arthroscopic synovectomy is comparable to synovectomy by arthrotomy in short term reduction of pain and swelling. The chief benefit of arthroscopic synovectomy is a reduction in morbidity, hospital stay and postoperative rehabilitation.