The hydrodynamic model for a liquid-solid classifier, developed by Chen et al. (2001), is applied to the steady state dispersion of mono-size, binary and multi-size particles in a liquid fluidized bed classifier. For the binary and multi-size systems, the particles had different sizes but equal densities. The model was used to investigate the effects of different operating conditions-fluidizing liquid flowrate, feed voidage, feed flowrate, underflow discharge flowrate, breadth of particle size distribution in feed stream, height of cylindrical region of the classifier-on the voidages in the underflow discharge stream and the overflow stream from the classifier, as well as classifier efficiencies. The single fitted parameter, an axial dispersion coefficient, is either fitted for a single condition using measured voidages or concentrations, or is based on a correlation given in an earlier paper. Predictions from the model agree quite well with the experimental results obtained in five columns of diameter 191 mm having different geometries with water and glass beads of different sizes.