The mass transport rates to planar electrodes, in a series of electrochemical laboratory filter-press reactors were measured to quantify the effects of the inlet and outlet design manifolds on the fluid flow. In small reactors, entrance/exit effects are especially important due to the localized generation of fluid recirculation zones, which affect the overall rate of mass transport. Limiting current data, the cathodic reduction of Cu(II) ions on a copper surface (under convective-diffusion control) were used to measure global mass transport coefficients. The data are compared with those from a well-characterized laboratory cell, the FM01-LC electrolyzer. The importance of manifold design in small-scale electrochemical reactors is discussed, and several dimensionless parameters are used to characterize the manifold geometry. (c) 2008 American Institute of Chemical Engineers.