We report a complication following trapeziectomy and tendon interposition. Subcutaneous herniation of the tendon interposition occurred in 3 of 412 cases in which trapeziectomy, ligament reconstruction, and tendon interposition were performed. This herniation occurred posterolaterally in the early postoperative period and resulted in dorsal swelling and superficial pain. Magnetic resonance imaging was helpful in confirming the diagnosis and excision of the herniated interposition material resulted in satisfactory pain relief and functional outcome as long as metacarpal stability was present. (J Hand Surg 2001;26A:444-447. Copyright (C) 2001 by the American Society for Surgery of the Hand.)