The Darrach and Sauvé-Kapandji procedures are considered to be useful treatment options for distal radioulnar joint disorders. Postoperative instability of the proximal ulnar stump and radioulnar convergence, however, may cause further symptoms. From October 1999 to May 2002, a total of 19 wrists in 15 men and four women, with an average age of 48.3 years, were treated by stabilizing the proximal ulnar stump with a half-slip of the extensor carpi ulnaris tendon using modified Darrach and Sauvé-Kapandji procedures. The average follow-up period was 77 months (range, 62 to 91 months). No patient complained of symptoms due to instability of the proximal ulnar stump. Grip strength improved in all wrists after surgery. Postoperative X-rays, including loading X-rays, showed improved alignment in both coronal and lateral planes. We concluded that stabilization of the proximal ulnar stump with ECU tenodesis is an effective procedure for treating distal radioulnar joint disorder after the Darrach and Sauvé-Kapandji procedures.