Dimethyl ether (DME) is a potential fuel for direct oxidation fuel cells that combines the main advantages of hydrogen (pumpless fuel delivery) and methanol (high energy density storage). DME also has low toxicity compared to methanol, making it a potential fuel for portable applications. This paper describes performance aspects and limitations of the DME fuel cell. At the anode, there is a critical balance between water and DME availability for reaction that suggests a thin electrolyte to promote back diffusion of water to the anode is desirable for high performance. However, excessive DME or DME intermediate crossover reaction losses with a Pt/Ru anode and Pt cathode catalyst preclude use of the thinnest electrolytes available. (C) 2003 The Electrochemical Society.