Operation of proton exchange membrane fuel cells at high current densities is a potential option to reduce fuel cell cost and volume for automotive applications. This operating regime was investigated using low cell voltages leading to limiting current density values. A zero-dimensional cell voltage model and a one-dimensional low cell voltage model were developed and validated. The operating conditions required for model applicability were summarized. The gas diffusion electrode overall mass transfer coefficient was identified as a key design parameter. (c) 2006 The Electrochemical Society.