This paper discusses the laws of the fuel consumption in a polymer electrolyte fuel cell and its related performance. Based on simplifying but realistic approximations these laws are presented in analytical form. We verify these laws with space resolved current-voltage measurements in a single channel fuel cell. The results give a clear picture of the inside-the-cell distribution of performance associated with reactant consumption. This picture helps to rationalize the modes of optimal fuelling and is lessening for design of the flow-fields. (C) 2004 Elsevier Ltd. All rights reserved.