The influence on the wrist stability following ulnar head resection (Darrach s procedure)was studied. A series of X-ray films and arthrography of the wrist joint were taken before and after ulnar head re- section. The results showed that after ulnar head resection the radial deviation increased 3 degree(Plt;0.01). and the ulnar deviation 11.92 degree (Plt;0.001). The position of the lunate remained unchanged. Arthrography of the wrist joint demonstrated that 11 specimens had injury of the triangular fibrocartilage.The stability of the wrist joint would no doubt be certainly affected following the ulnar head resction.