Oxygen uptake in the black-lip pearl oyster Pinctada margaritifera was examined with the direct measurement method of ventilation volume at 27 ℃ . The ventilation volume maintained the same level as that (0.385 l/min/kgTW: total weight) under normoxic condition until the oxygen partial pressure (Po_2) decreased to 115.1 mmHg, then it increased to 0.677 l/ min/kgTW (1.8 times the normoxic ventilation volume) at 22.0 mmHg. The oxygen utilization maintained the same level as that (3.7%) under normocic condition until Po_2 decreased to 115.1mmHg, then it increased to 15.0% at 9.9 mmHg. The amount of oxygen uptake maintained the same level as that (0.068 ml/min/kgTW) under normoxic condition until Po_2 decreased to 61.6 mmHg, then it decreased when Po_2 further declined.