The purpose of this study was to investigate the functional recovery of end-to-side neurorrhaphy in rats. There have been several studies about the results of end-to-side neurorrhaphy from a histologic or eletrophysiologic view point. However, histologic or electrophysiologic parameters may not correlate with the actual nerve function. In this study we assessed the results of end-to-side neurorrhaphy functionally using walking track analysis. Forty-eight male Sprague-Dawley rats were randomly divided into 4 group, with 12 rats in each group. Group 1 was the sham-operation group. Group 2 was the peroneal nerve transection group. In group 3, the peroneal nerve was severed and end-to-end neurorrhaphy was carried out. In group 4, the peroneal nerve was severed and coapted end-to-side to the lateral face of the tibial nerve after removal of the epineurium arid perineurium. Walking track analysis was done every 2 weeks up to 16 weeks. Group 3 recovered 80.4% in peroneal function at postoperative 16 weeks, whereas group 4 recovered only 46.0%. In group 2, it was impossible to measure the peroneal function by walking track analysis because of plantar flexion contracture after 6 weeks. We concluded that the end-to-side neurorrhaphy group showed better results compared with the nerve transection group. However, the end-to-end neurorrhaphy group showed still better results in the walking track analysis of rats.