In this work, the transition between conventional dense-phase spouting and dilute-phase spouting is quantified and characterized on the basis of experimental particle velocity and bed voidage data, obtained with an optical fiber probe, as well as from the evolution of pressure with air velocity The high gas velocities associated with the dilute-phase spouted bed (DSB) flow regime result in voidages exceeding 0 9 over the entire bed, with no discernible distinction between spout and annulus The downward particle velocities for the DSB regime differ in magnitude from those in the dense-phase spouting regime. Computational fluid dynamics simulations using the Eulerian granular multiphase model show good agreement with experimental data for the three reproducible flow regimes: dense-phase spouting, transition regime, and dilute-phase spouting.