In this paper results are presented from four different particle size analysis techniques used to characterize the performance of a novel centrifugal gas-solid separator. The Post Cyclone (PoC), is a new secondary collector situated at the top of a conventional reverse flow cyclone which utilizes the residual swirl available at the outlet (vortex finder) to capture some of the escaped dust. A prototype PoC was tested for a Stairmand high-efficiency cyclone (diameter = 0.4 m) under a range of operating conditions. It is inherent to the process that the size distributions of the captured and escaping dust from the PoC are very close, Moreover, only little dust bigger than 5 mu m escaped from the cyclone to the PoC, making grade efficiency curves unreliable above this particle size. This means that demands on the quality of the particle sizing for this application are especially strenuous. Therefore, four different types of analytical equipment, namely a disc centrifuge, a cascade impactor, a cyclone train and a laser scattering sizer were used to collect information about the size distribution of the particles. This work highlights the apparent merits and shortcomings of each of these methods and compares the experimental grade efficiencies obtained by the different methods. (C) 2000 Elsevier Science Ltd. All rights reserved.