The gas induction characteristics of a stator-rotor-type self-inducing impeller were investigated in the cases without and with gas line resistance. To understand the hydrodynamics near the impeller, and to characterize the mechanism of gas induction, the local liquid velocity was measured with a laser Doppler anemometer. The effect of impeller speed, impeller submergence, and gas line resistance on the volumetric flow rate of liquid, as well as the rate of gas induction, was investigated. The dominant role of local gas holdup was identified and the mechanism of gas induction was established, with the help of an energy balance.