The residence time distribution (RTD) of solids in spiral fluidised beds was experimentally investigated, covering as variables the flow rates of the phases, the particle characteristics and the column and plate geometries. The RTD was adequately described by the Fickian diffusion model, indicating that particle dispersion can be predicted from a knowledge of particle diffusivity. Correlations for the particle mean residence times and the particle diffusivity are presented. © 1989.