BACKGROUND After a peripheral nerve cut, tense repair of a nerve compromises circulation of the nerve at the injury site, making the site hypoxic. Hyperbaric oxygen might increase tissue oxygenation and therefore diminish the effects of injury. We investigated whether hyperbaric oxygen treatment affects peripheral nerve healing when repaired nerves are under tension. METHODS Sixteen young female albino Wistar rats were used. Sciatic nerves of the animals were cut and a 3mm part of each nerve was excised. The animals were distributed into two groups: 1) The HBO2 group (n = 8), which received surgical repair and HBO2 therapy; and 2) The Control group (n = 8), which received only surgical repair. Walking track analysis was performed five times, on Days 12, 15, 18, 20 and 22 after surgery. The healing of sciatic nerves was evaluated by histopathological study and electrophysiological study. Pillai's Trace test and Mann-Whitney U-test were used for statistical analysis. RESULTS Walking track analysis: Sciatic function index (SFI) scores of HBO2 group were significantly higher than SFI scores of Control group (p:0.026). Electrophysiological study: A statistical difference was not found between groups. Histopathological study: Counts of HBO2 group axons were significantly greater than in the control group (p: 0.008). CONCLUSIONS In clinical practice, tension after nerve repair frequently occurs. However, neither grafting nor other current surgical methods are functionally perfect. Since primary end-to-end repair is known to be the best repair when possible, we think HBO2 allows for the use of primary repair even when nerve tension is foreseen.