Direct dimethyl ether (DME) fuel cells suffer from poor DME–water miscibility and so far peak powers of only 20–40 mW cm⁻² have been reported. Based on available literature on solubility of dimethyl ether (DME) in water at ambient pressure it was estimated that the maximum concentration of DME at 80 °C will be 300–600 times lower than the ratio 1 to 3 which is the stoichiometric ratio for full conversion to CO2. To overcome this dilution problem a high temperature polymer fuel cell was operated on DME–water vapor at ambient pressure and with air as oxidant. A peak power density of 67 mW cm⁻² was measured at 200 °C. A series of performance curves at temperatures ranging from 150 to 250 °C showed a pronounced temperature effect on the performance. Comparison was made between performances as direct DME and direct methanol cells and the difference was not as large as normally seen with conventional liquid fed cells below 100 °C.