A theoretical analysis has been performed in this study for a novel design of membraneless microfuel cell utilizing a Y-shaped microchannel. Hydrogen peroxide is employed both as fuel and oxidant and dissolved in dilute sodium hydroxide and sulfuric acid solutions, respectively. The anode and cathode liquid streams enter the Y-shaped microchannel separately at different inlets and then flow in parallel through the microchannel without occurrence of turbulent mixing on the contact interface of both streams. The decomposition of hydrogen peroxide in both streams will generate electric power. Such a novel design eliminates the need of a membrane to partition the two liquid streams. The cell performance was investigated in detail by examining the important system parameters such as the concentration of reactant, volumetric flow rate, thickness of catalytic layer, length of microchannel, and geometric design of electrodes. Results provide physical insights for the effects of these parameters on the cell performance and benefit the optimal design of this type of microfuel cell as well as the fulfillment of its application in portable power sources. (C) 2007 Elsevier Ltd. All rights reserved.