We report results from a computational study of the transition from bubbling to slugging in a laboratory scale fluidized-bed reactor with Geldart Group B glass particles. For simulating the three-dimensional fluidized-bed hydrodynamics, we employ MFiX, a widely studied multi-phase flow simulation tool, that uses a two-fluid Eulerian-Eulerian approximation of the particle and gas dynamics over a range of gas flows. We also utilize a previously published algorithm to generate bubble statistics that can be correlated with pressure fluctuations to reveal previously unreported details about the stages through which the hydrodynamics progress during the bubbling-to-slugging transition. We expect this new information will lead to improved approaches for on-line reactor diagnostics, as well as new approaches for validating the results of computational fluidized-bed simulations with experimental measurements. (C) 2016 Elsevier B.V. All rights reserved.