We prospectively studied a consecutive series of 25 knees (21 patients) treated with arthroscopic synovectomy for seropositive rheumatoid arthritis. All patients had pain and swelling and were in the early stages of the disease process (Larsen grade 2 or less). Three patients were lost to follow-up. At a mean of 8 years from operation two knees underwent total knee replacement with another two knees required a further arthroscopic synovectomy. One patient continued to experience intermittent mild synovitis. The range of movement was maintained or improved by surgery in 73% of cases but radiological evidence of degenerative change was seen in all knees. We discuss the technical difficulties associated with arthroscopic synovectomy that were associated with a small complication rate. In appropriately selected patients unresponsive to medical therapy, arthroscopic synovectomy can give safe and reliable results.