The peroneal tendons are located within a fibroosseous tunnel at the posterior aspect of the distal fibula. Peroneal tendon instability, which is rarely encountered, was first described in 1803 by Monteggia in a balet dancer. A twenty-year-old male patient referred to our clinic with pain at the lateral side of his right ankle during motion. History revealed that patient had ankle sprain 6 months before presenting to our clinic. After clinical examination and radiologic assessment, peroneal tendon instability was diagnosed and surgical treatment was performed. In the present study, we aimed to present the results of our surgical teratment as well as the functional outcomes of the surgery.©2005, Fırat Üniversitesi, Tıp Fakültesi