Both radial tunnel syndrome and posterior interosseous nerve (PIN) compression syndrome are caused by compression of the posterior interosseous nerve. There is a controversy about certain features of PIN compression especially with regard to diagnostic criteria and therapy as well as differentiation from tennis elbow. From 1992 to 1997, we operated 110 patients because of PIN compression. Diagnosis was based on clinical examination only. As a rule, we decompressed the PIN directly using an anterior approach. With regard to radial tunnel syndrome, we could review 69 from 103 operations with an average follow-up of 41 months. Using the criteria originally proposed by Roles and Maudsley, only 60% showed excellent or good results. The mean DASH score was 32. Recompression of the PIN by scarring was found in as much as 17% of patients and proved to be a serious complication of direct decompression of the PIN. Furthermore, 52% of our patients operated on because of PIN compression suffered from tennis elbow as well. We therefore believe that radial tunnel syndrome is a specific form of tennis elbow. From an anatomical point of view, the inseparable origin of the radial wrist extensors and supinator muscle seems to link tennis elbow and radial tunnel syndrome. To avoid recompression of the PIN by scarring, we have abandoned direct decompression and now routinely use Wilhelm's denervation procedure for the treatment of tennis elbow as well as radial tunnel syndrome. This procedure indirectly decompresses the PIN by cutting the superficial origin of the supinator muscle with consecutive relaxation of Frohse's arcade. Preliminary results are promising and show improvement of preoperative neurologic status by indirect decompression.