In this study, particle image velocimetry (PIV) technique was employed to measure the flow field in the rotor zone of an annular centrifugal contactor (ACC). The velocity distribution and streamline diagrams of the flow field relative to the stationary reference and rotating reference frame was investigated as well. It was found that the fluid formed a vortex in each separation cell relative to the rotating reference frame. The magnitude of the tangential velocity and that of radial velocity significantly changed with the speed of rotation. The flow rate had insignificant impact on the tangential velocity and the radial velocity. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.