Purpose. Idiopathic Carpal Tunnel Syndrome (CTS) is the most common entrapment neuropathy; however few and only retrospective studies have been found in search engines about Ozone Therapy. The aim of this paper was to evaluate clinical and neurophysiological outcome following Ozone Therapy in CTS. We focused the attention on the evidences concerning the role of Subsynovial Connective Tissue (SSCT) in the pathogenesis of CTS and the ozone pre-conditioning effects linked to pain and inflammatory pathways and to fibrosis induced by Ischemia-Reperfusion Injury. Materials and methods. Thirty-five patients, aged between 21 and 80, were stratified clinically by Boston Carpal Tunnel Questionnaire (B.C.T.Q.) and Neurophysiologically by Padua?s Gravity Scale classifying patients into five Electro-myographic categories. The mean symptom duration was also recorded. The patients filled in the B.C.T.Q. before and after treatment as well underwent diagnostic neurophysiological tests, strictly standardized in stimulation parameters, electrodes placement and skin temperature. The Ozone Therapy was performed by injecting 4 ml of O2-O3 mixture at 10 ug/ml concentration under the transverse carpal ligament twice a week for eight sessions. Results. We compared the B.C.T.Q. scores and the neurophysiological parameters obtained before and after O2-O3 treatment: the improvement of symptoms was significantly greater than the improvement of motor and sensory nerve conduction. The highest clinical improvement degree was found in patients classified in Mild and Moderate Groups. Discussion and Conclusion. Ischemia-Reperfusion Injury triggers oxidative stress in SSCT with activation of chemical mediators and neo-angiogenesis leading to non-inflammatory fibrosis that represent the allmark of CTS. Previous and retrospective studies based O2-O3 treatment on the main mechanisms of action shared by the treatment of herniated disc in the spine; our study focused the attention on pathophysiology of the SSCT trying to recognize the various stages of CTS pathogenesis by correlating with clinical and neuro-physiological tests. Further studies have to be carried out to better understand these relationships and optimize timing of Ozone Therapy.