The dynamics and structure of a fluidized bed in inclined columns are investigated experimentally. Experiments were conducted in two glass columns of L/D = 95 and 150, and diameters of 2.58 and 2.78 cm, which can be positioned in the whole range of inclination angles, from horizontal to vertical. The fluidizing agent is water and the grain material is particles of different densities and characteristic diameters. Measurements of the pressure loss, flow rate of the fluidizing agent and fluidized bed position and height are carried out. Particle flow patterns were visualized using a digital camera. The expansion process of the fluidized bed depends strongly on the inclination angle. Consequently the critical velocity for the bed escape varies with the column inclination angle and exhibits a maximum at about 45 degrees. The column length was found to have a minor effect on the phenomena involved. (c) 2006 Elsevier B.V. All rights reserved.