Two novel techniques to measure velocity in opaque pulp fiber suspensions have been evaluated in a hydrocyclone. A pitometer equipped with a medical micropressure transducer was used to record the tangential velocity. The pressure opening of the pitometer was kept clean with a small purge flow. The small size of the probe minimized its influence on the flow field. The pitometer was able to measure the tangential velocity in the fiber suspension at different levels in the hydrocyclone. Additionally, a non-intrusive ultrasonic velocity profiler (UVP) was used to measure the radial particle velocity. The UVP proved to be capable of measuring radial particle velocity profiles. (C) 2004 Elsevier Ltd. All rights reserved.