Mass transfer coefficients at electrodes positioned in the walls of a flow channel containing a fluidised bed of inert particles were determined electrochemically by measurement of limiting current for the diffusion controlled reduction of Fe(CN)(6)(3-). The electrodes were positioned 30cm above the bed support thus minimising bed entrance effects and assuring only fluidisation enhancement of wall mass transfer rates. Spherical glass particles in the size range 0.6 to 1.5mm were employed and data were correlated in the range 5 < Re-dp/(1 - epsilon) < 2000 by the equation j(D) epsilon = 0.28[Re-dp/(1 - epsilon)] (-0.36) Comparison is made with data from several other sources. Experiments were also conducted in the packed bed condition and also for empty channel flow. Hydraulic aspects of fluidised bed performance were also investigated. The relative merits of the Zaki and Richardson and the Aerov and Todes equations for the superficial velocity - porosity relationship and minimum fluidisation velocity conditions being critically evaluated.