Abstract Semifluidized bed hydrodynamics, including minimum semifluidization velocity, packed bed formation and pressure drop across the bed, were studied in gas-solid fluidized beds. Experiments were carried out in beds of 0.203, 0.139 and 0.105 m I.D. Experimental parameters examined included gas velocity, semifluidized particles, static bed height and expansion ratio. Empirical and semi-empirical models were derived. The results were compared with those available in the literature.