A 10-cell high-temperature polymer electrolyte fuel cell (HT-PEFC) stack with an active cell area of 200 cm2 has been built up and tested with regard to the temperature distribution from cell to cell and over the active area since not every cell is cooled. Measurements with artificial reformate as a fuel show that the vertical temperature distribution over the active area is sufficiently small, with a maximum of 5.1 K at 550 mA cm−2. Additionally, the temperature gradient from cell to cell is sufficiently small with 10.7 K at 550 mA cm−2. As a result, it can be concluded that the heat pipe supported external cooling is well suited to cool HT-PEFC stacks with large active areas in reformate operation.