The cross-flow model (Chem. Engng Sci. 1973 28 585), proposed by the authors for multistage systems, is matched with the experimental data taken subsequently on the residence time distribution of solids in a multistage fluidised bed. The model parameters are related to the plate geometry and the flow rates of the phases. The model is found to agree with the experimental data of the earlier investigators on single and multistage fluidised beds with a maximum root mean square deviation of 0·05. Based on the data, conditions for smooth fluidisation are suggested. © 1975.