Bubbling and slugging were investigated in a 0.05 m internal diameter bed of Geldart group A powders. The slugging characteristics were assessed in terms of the operating parameters. Neither bed height nor particle properties affect the excess gas velocities at the onset of slugging, as predicted by the Stewart criterion. Slugging characteristics (length and frequency) and fluidized bed properties were determined. The bottom zone of the bed is freely bubbling, and the bubble sizes can be predicted by d(B) = 0.047Ha(0.37), where dB is the frontal diameter of the bubble and H is the fluidized bed height. Mostly, wall slugs occur higher in the bed when dB exceeds about 50% of the column diameter. The slug frequency varies with the height in the bed but reaches an equilibrium value of 1 Hz for bed heights exceeding m. Three distinct zones appear in a deep bed of group A powders. The design and scale-up should combine the bubbling and slugging modes within their corresponding regions in the bed.