A catalytic burner (CAB) was developed, which utilizes the anode off-gas of a high temperature polymer electrolyte fuel cell (HT-PEFC). This CAB has two functions within the HT-PEFC-system: It has to convert completely all combustible components including methane and carbon monoxide, even in the low ppm range and it has to provide steam to the autothermal reformer (ATR). Thereby it increases the system's overall efficiency. Using computational fluid dynamics and experiments with a simple glass model, two catalytic burners (CAB 2 and CAB 3) were designed and constructed for a high temperature PEFC system with thermal powers of 18 kW and 28 kW, respectively. The burners were characterized experimentally in detail. Close attention was given to the steam generation capacity and the thermal behavior. The constructed burners allowed complete conversion of low calorific fuel gases and a reformate in part load of the ATR was burned reliably as well. Superheated steam was generated free of oscillation. Experimental findings with CAB 2 resulted in an improved reactor generation with a reduced specific weight and geometric changes. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.