Data are presented to show the transient response of a proton exchange membrane fuel cell (PEMFC) subjected to change in the load. Overshoot and undershoot behaviors of the steady-state current density were observed for various rates of change in the voltage during constant inlet flow rate conditions. The results of these experiments with a 25 cm(2) triple serpentine flow field indicate a correlation of the overshoot/undershoot behavior with initial and final stoichiometry. This transient analysis is potentially attractive in the operation of vehicle and stationary application and flow field designs. (C) 2004 Elsevier B.V. All rights reserved.