The aim of this work was to investigate the mixing of pseudoplastic fluids possessing yield stress by studying the effect of power consumption, yield stress, impeller type, and impeller clearance on the mixing time. Using these results, it was desired to put together a proposal for mixing system configuration that would form the basis for mixing system optimization. To that end, computational fluid dynamics (CFD) modeling and experiments were performed. in order to determine the capability of CFD to forecast the mixing process, ultrasonic Doppler velocimetry (UDV), which is a non-invasive flow measurement technique for both opaque and transparent fluids, was used to measure fluid velocity. It was observed that the numerical results were in good agreement with the experimental data. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.