Sieved silica-alumina particles (diameter = 481 mu m; density = 1990 kg/m(3)), glass beads (diameter = 516 mu m; density = 2500 kg/m(3)) or mixtures thereof were fluidized in a vertical bubble column of 7 cm in diameter and 4.50 m in height. The bed was operated batchwise or continuously with respect to the feed of solid particles. Axial changes in gas and solid holdups in the bed were measured by simultaneously sectioning the column with 20 horizontal plates. The measured solid holdup of each component in the column was compared with the analytical results calculated by a one-dimensional sedimentation-dispersion model. Both experimental and calculated results were in satisfactory agreement over the entire column, which consisted of dense and dilute regions, as well as circulating quantities of liquid and solid particles.