We evaluate the performance of a relatively efficient cyclone operating under conditions analogous to a generic pressurized circulating fluidized bed at high solid loading. We find that pressure losses across the cyclone scale with the kinetic energy density of the inlet gas and are independent of the particle Stokes number and the Reynolds number based on cyclone diameter. The pressure data are well captured by the model of Muschelknautz and Greif (1997), who predict that the corresponding losses decrease with increasing solid loading. We confirm that the overall cyclone solid capture efficiency and the efficiency by size depend on the particle Stokes number and loading. We find that the effects of these two numbers are complex and not well captured by existing models, which, unlike experiments, assume a uniform distribution of solids at the inlet. (C) 2004 Elsevier Ltd. All rights reserved.