A liquid (heat transfer oil) cooling system for high temperature polymer electrolyte fuel cell (HT-PEFC) stacks in the power range above 1 kW(el) using encapsulated cooling cells was designed. Calculations showed that it is sufficient to cool every third cell to maintain an operating temperature of about 160 degrees C. An HT-PEFC stack module including 12 cells with an active area of 320 cm(2) each was assembled and tested experimentally regarding the temperature distribution from cell to cell. It was found that sufficient cooling with an oil inlet temperature of 160 degrees C is guaranteed up to a current density of 450 mA/cm(2) when operated with synthetic reformate (42% H-2, 57% N-2, 1% CO). At this current density, the maximum temperature difference from cell to cell does not exceed 8.3 K. Additionally, this cooling system provided enhanced protection against leaks. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.