A thermal-electrochemical coupled model is presented to predict electrochemical and heat transfer behaviors in a proton exchange membrane (PEM) fuel cell. The Brinkman extension to Darcy flow describes the fluid flow characteristics in the porous electrodes. The Stefan-Maxwell correlations together with the Bruggemann modification illustrate the multispecies diffusion in the porous electrode. A two-equation approach is used to account for the local thermal nonequilibrium between the solid matrices and the fluids in the gas diffusion layers. In the catalyst layers, the heat dissipation due to irreversible-process heating is determined from the macroscopic electrochemical model. The present model is capable of simultaneously predicting the solid phase temperature and the fluid phase temperature inside the fuel cell, which enables a comprehensive understanding of the mechanisms responsible for thermal pathways. Most importantly, it has successfully assessed the possibility of hot spots within a PEM fuel cell. Increasing the interfacial heat-transfer coefficient between the solid phase and the fluid phase (h nu) from 1.0 x 10(3) to 1.0 x 10(6) W/m(3) K has an advantage of alleviating the hot spot. Thermal effects on the active material degradation and hence fuel cell cycle life will be incorporated in the future work. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.2137652] All rights reserved.