The effect of gas sparging on the rate of mass transfer at a vertical single screen was studied by an electrochemical technique which involved measuring the limiting current of the cathodic reduction of potassium ferricyanide. Variables studied were screen characteristics, physical properties of the solution and gas superficial velocity. Screen characteristics, e. g., mesh number and wire diameter were found to have little effect on the rate of mass transfer. The data at different screens were correlated in terms of the superficial gas velocity by the equation St Sc-0.5 = 0.095 (Re Fr)(-0.272) where St is Stanton number, Sc is Schmidt number, Re is Reynolds number and Fr is Froude number. Comparison of the present data with previous results obtained with different transfer geometries has shown that screens produce higher rates of mass transfer than other geometries. The importance of the present work to catalytic and electrochemical reactor design was noted.