Particle velocities have been measured in two-dimensional water fluidized beds of mono-sized spherical glass particles d(p) = 1.94, 2.98, 4.00 and 6.00 mm in diameter. For each particle size, a separate column was constructed in a manner that the column thickness corresponded to approximately 3 particle diameters. A large number of observations are required to obtain a stable value of total particle speed. The presented data indicated that in order to obtain a stable value of the mean total particle speed, a minimum of 4000 data points was needed. The distribution of total particle speeds follows the Maxwell distribution quite well. The effect of water velocity on the distribution function was similar to the effect of temperature on molecular speed distribution in the kinetic theory. The distribution of vertical and horizontal particle velocity components followed approximately a modified Gaussian distribution. A correlation for predicting the total mean particle speed in 2D water fluidized beds is proposed. The mean absolute deviation between the experimental and measured particle velocities for the present data is 11.0%. The proposed correlation predicts the data of Carlos and Richardson [5] and Latif and Richardson [6] for 3D fluidized beds reasonably well. (C) 2013 Elsevier B.V. All rights reserved.