Water electrolysers using proton exchange membranes (PEM) offer high prospective potentialities for the production of pure hydrogen. Main components of PEM cells are (i) solid polymer electrolyte, (ii) electrocatalytic layers, (iii) porous current collectors and (iv) bipolar plates used to separate individual cells. The work presented in this paper is devoted to the optimization of the microstructure of current collectors, the role of which is to provide efficient electric contact between electrocatalytic layers and bipolar plates and to insure efficient gas/water transport between them. Optimum pore sizes, plate thicknesses and porosities of current collectors have been determined from both experimental and modeling approaches, for operation at high current densities (up to 2 A cm(-2)) in PEM water electrolysis cells. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.