Bubbling fluidized bed experiments were performed on powders ranging in size from 0.012 to 15 mu m, with room temperature air as the fluidizing gas. Powders this fine are cohesive in nature and typically form clusters of particles, which can interfere with the fluidization process And, in some cases, result in channeling and spouting, instead of bubbling. Previous studies in our laboratory explored the use of high intensity acoustic vibrations to disrupt the interparticle forces and decrease the superficial gas velocities needed to achieve minimum fluidization. The present paper deals with the simultaneous use of acoustics and horizontal mechanical vibrations to achieve fluidization. Experiments were run with the bed equipped with a loudspeaker at the top of the freeboard and a motor driven mechanism to impart horizontal vibrations to the fluidized bed column. Results are presented on the effects of these two types of vibrations on minimum fluidization. (C) 2006 Elsevier B.V. All rights reserved.