The influence of operating pressure on the motion of particles near the fluidized-bed wall surface was studied for Geldart group A and B particles using luminescent pigment as bed solids in a vessel of diameter 146 mm. A pulse of bright light transmitted from outside the pressure vessel via fiber optics was used to illuminate a 7-mm-diameter region of the bed particles adjacent to a transparent vessel wall. Digital image analysis of the motion of the illuminated region of bed particles and its decay in luminosity permitted the determination of the influence of pressure on a particle exchange frequency in the direction perpendicular to the wall surface, the mean particle residence time at the wall, and the velocity of bed solids adjacent to the wall. These findings are related to the observations of the effect of pressure on bed-to-surface heat transfer in fluidized beds reported by other workers.