Synovectomy has been recommended as an effective procedure in many cases of the synovial proliferative diseases. This study was undertaken to evaluate the efficacy of the intraarticular synovectomy with arthroscopic technique. Ten knees of the nine patients operated in Seoul National University Hospital from March 1987 to June 1991 were studied. Of the nine patients, six were females and three were males, five knees were affected on the right and five on the left respectively. Mean age at the time of operation was 28.8 years. Of the ten knees, six knees were diagnosed as rheumatoid arthritis and four knees as chronic nonspecific synovitis. After operation, the patients were evaluated using clinical data including pain relief, range of motion and presence of effusion. Average hospital stay after operation was 9 days. Average operation time was 71 minutes. After average follow-up of 26 months, eight knees showed good results and two showed poor results. Of the two poor knees, one showed persistent pain, the other showed recurrent effusion and persistent pain. No complications occured as a result of these synovectomies. In summary, arthroscopic synovectomy improved important symptom such as pain and effusion of the chronic synovitis without loss of range of motion and also with improved activity. Results of this study suggest that arthroscopic synovectomy yields reliable result comparable to open synovectomy with less invasiveness and postoperative morbidity.