"We undertook this study to investigate the adequate oxygen concentration that can be applied safely to the treatment of pneumothorax. Complete unilateral pneumothorax was induced artificially in rabbits, which were subsequently treated with various inspired oxygen fractions (FIO₂; 21%, 60%, 80% or 100%). The pneumothorax resolution time was measured together with the levels of IL-1β and IL-8 in broncho-alveolar lavage (BAL) and plasma samples. Furthermore, the lungs from these animals were examined for histolopathological evidence of oxygen toxicity. The results showed that the resolution time was significantly faster in the pneumothorax rabbits when treated with higher FIO₂. Significantly higher levels of IL-1 β were detected in BAL samples collected from the pneumothorax-rabbits that had received FIO₂ at levels of either 80% or 100% (P < 0.05), but not in those with FIO₂ at the 60% level. However, there was no significant change in the level of IL-8 in the BAL when the pneumothorax-rabbits were treated with different FIO₂ levels. In addition, no evidence of oxygen toxicity was found when the lung tissues were examined. The data indicated that higher FIO₂ treatment can accelerate the resolution of pneumothorax, but caution should be exercised with regard to associated oxygen toxicity when the FIO₂ used is greater than 80%. We conclude that treatment with 60% FIO₂ is an appropriate concentration for oxygen therapy for the treatment of pneumothorax in this model."