A numerical and experimental characterization of the performance of a High Temperature Polymer Electrolyte Membrane Fuel Cell (HT PEM FC) is presented. Starting from the fluid dynamic optimization performed in a previous work, a detailed 3D CFD-electrochemical model of a single HT PEM FC is developed, in order to describe the internal fluid dynamic fields coupled to the electrochemical reactions. To validate the numerical activity, an experimental campaign has been conducted on a single-cell prototype built ad-hoc, with both pure H-2 and Syngas anodic feeding. The results of both the numerical and experimental investigations are compared to the performance of commercial HT PEM Fuel Cells, proving the good accuracy of our numerical method as well as the consistency of the experimental setup. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.