In this study, we compared the performances and the operation stabilities of direct fuel cells fed with dimethyl ether (DME) gas and aqueous DME solution as fuel, respectively. The maximum power density of the cell with DME solution was 56 mW cm(-2), which was much higher than that of the cell fed with DME gas (38 mW cm(-2)). The electrochemical impedance spectra analyses revealed that the mass-transfer resistance of the DME solution was lower than that of the DME gas. The constant current operation curves showed that the performance decay rate of the DME solution was lower than that of the DME gas. It indicated that the direct dimethyl ether fuel cell fed with DME solution benefited the long-term operation. (C) 2008 The Electrochemical Society.