INTRODUCTION: Radial ulnar synostosis is the most common complication of the two-incision biceps repair. Thus far, only one study in the literature has described this complication and treatment thereof. MATERIALS AND METHODS: Between 1992 and 2000, 8 patients with radioulnar synostosis after a two-incision biceps repair were evaluated and treated by the senior author, with a mean age of 38 (range 29-47) years old. The mean time between tendon repair and resection of the synostosis was 8 (6-18) months. The average follow-up was a 27 (range 13-36 months). An average pronation-supination arc of 27o (range 0 o – 70 o) was noted preoperatively. Postoperatively all patients underwent post-operative radiotherapy in two divided doses for a total of 700 rads. Operative Technique: The posterolateral incision was extended an the interval between the extensor digitorum comminis and the extensor carpi radialis brevis is developed to expose the supinator muscle. The posterior interosseous nerve is identified and protected. The synostosis is subperiostaly exposed through a separate interval, from the ulna to the radius. RESULTS: At an average follow-up of 27 months, it was noted that the rotation arc of the forearm improved to 155 o (range 140 o – 170 o) with an average gain of 128 degrees. The strength of supination was 80% (range 70% - 90%) of the contralateral limb. Seven of the eight patients had no pain after activities of daily living or work. One had mild pain after prolonged activity. No radiographic or clinical evidence of synostosis recurrence was noted at final follow-up. CONCLUSION: Based on our results we believe that resection of early radioulnar synostosis can be effectively achieved through one posteriolateral incision and postoperative radiotherapy.