Two hundred sixty-four patients with rheumatoid arthritis were treated with 901 Swanson silastic arthroplasties of the metacarpophalangeal joints. Average followup was 8 years with a minimum of 2 years. Preoperative ulnar deviation averaged 45 degrees and improved to an average of 15 degrees postoperatively. Active flexion arc averaged 40 degrees preoperatively and 50 degrees postoperatively, an increase of 10 degrees. The extensor lag postoperatively improved to 10 degrees from 50 degrees preoperatively, placing the arc of metacarpophalangeal joint motion between 10 degrees and 60 degrees flexion. Complications included dehiscence and delayed wound healing (2%), superficial infection (0.5%), deep infection (3%), and prosthetic fracture (14%). Subjectively, most patients thought that their postoperative function was improved. This was thought to be attributable in part to the correction of the ulnar deviation deformity of the fingers, and the shifting of the arc of motion of the metacarpophalangeal joints to one allowing increased metacarpophalangeal extension, thereby improving the opening capacity of the digits and the overall function of the hand.