The filtering hydrocyclone is a solid-liquid separation device consisting of a hydrocyclone whose conical section is replaced by a conical filtering wall, which was patented by the Federal University of Uberlandia, School of Chemical Engineering (Brazil). During the operation of these separators, besides underflow and overflow streams, the filtering process generates a stream of filtrate in the hydrocyclone's permeable conical region. The main purpose of this work was to analyse the fluid dynamic behaviour of filtering hydrocyclones based on simulation and experimental studies. The simulations were done in conditions that were symmetric in relation to the central axis, using rectangular grids. The FLUENT 6.1.22 (R) simulator was used to solve the transport equations. The results indicated that the performance of hydrocyclones is significantly influenced by the filtering medium. The incorporation of the filtering medium decreased the Enter numbers and increased the total efficiency of the hydrocyclones. (c) 2007 Elsevier B.V. All rights reserved.