The effect of hyperbaric oxygen on the proliferative and synthetic responses of fibroblasts derived from wounds and normal skin was examined in this study. Hyperbaric oxygen treatment resulted in a slight decrease in fibroblast proliferation but an increase in the synthesis of extracellular matrix components. Relating these results to the process of wound healing suggests that hyperbaric oxygen therapy would increase the matrix:cell ratio, which could have important consequences for repair processes such as cell migration and regulation of cell activity. There was no apparent difference in the response to hyperbaric oxygen of fibroblasts derived from different sources.