Local gas holdup was measured throughout an aerated vessel equipped with a Rushton turbine impeller by means of an electrical probe. Integration of the data of local gas holdup gave a good correlation for the overall gas holdup. The gas recirculation rate, which influences cavity formation and the related power consumption and mass transfer, was also determined by integrating the data of local gas holdup for regions lower than the height of impeller. By taking into account the gas recirculation rates, a more precise correlation for overall gas holdup could be obtained.