A monolithic hybrid direct methanol fuel cell (DMFC) with a novel configuration is proposed in an effort to reduce the weight and size of the conventional hybrid fuel cell system. A modified DMFC with a layer of hydrous ruthenium dioxide (RuO2 center dot xH(2)O) sandwiched between the anode catalyst layer and membrane has been used to demonstrate the principle of the monolithic hybrid DMFC. Experimental results indicate that the RuO2 l xH2O layer is equivalent to a resistive-capacitive transmission line and functions similar to a capacitor in parallel with the anode electrode. The improvement in dynamic response of the modified DMFC has been experimentally confirmed under square current pulse operating. (c) 2006 The Electrochemical Society.