Changes in trantcutaneous PO₂(tcPO, ) during water immersions with O₂ and N₂ bubbling are presented. Three healthy male volunteers underwent water immersions for 30 min. Water temperature was controlled to 36.5°C to minimize any thermal stress. Minute ventilation (Ve), oxygen consumption (VO₂), heart rate (HR), respiratory rate (RR), and body temperature (Tb) were continuously monitored throughout exposure. In addition, tcPO₂ electrode was mounted on the volar side of the right forearm in the middle part of immersion and tcPO₂ and tcPCO₂ were then monitored in the water, Blood flow of the right forearm was also measured following tcPO₂/tcPCO₂ meanurements. The tcPO₂ Values during water immersions with O₂ bubbling were higher than those with N₂ bubbling for given blood flow. Although end-tidal PO₂ remained unchangd for any occasion, Ve, VO₂, HR, RR during water immersions with O₂ bubbling were significantly decreased compared to those with N₂ bubbling. Results suggest that cutanuous respiration facilitated by hydration may contribute higher tcPO₂ Values during water immersions with O₂ bubbling and may be somewhat related to systemic changes.