Parameters on gas exchange in the gills were measured in eel acclimated for more than 2 weeks at 9.1±0.1, 25.8±0.6 and 33.5±0.2°C under normoxic and hypoxic condi-tions. Under normoxic condition, oxygen pressure of the dorsal aortic blood (Pa, o2) in-creased and pH of the blood (pHa) decreased as the temperature increased. Under hypoxic condition, pHa increased gradually, and Pa, o2 and oxygen content of the blood (Ca, o2) de-creased as the oxygen pressure of the water decreased. Under normoxic and hypoxic con-ditions, Ca, o2 at 25.8°C was the same as that at 9.1°C, but Ca, o2 at 33.5°C was smaller than that at both temperature. High Pa, o2 at high temperature must be a compensation for the detrimental effects of low pH and high temperature on the oxygen transport by the blood.