This contribution comprises a detailed description of the construction and performance characterization of a high temperature polymer electrolyte fuel cell stack. Specific features of the stack setup are the modular design and the cooling strategy with encapsulated cooling cells. Commercially available Membrane Electrode Assembly (MEA) and bipolar plate materials were used. The performance analysis includes a parameter variation for the fuel (pure hydrogen and synthetic reformate), anode and cathode stoichiometry's and operation temperature. Additionally the long-term behavior at constant load was investigated. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.