We prepared crystalline Ag nanocluster-incorporated RuO2 electrodes using a radio frequency magnetron cosputtering system for use in thin-film micropseudocapacitors and investigated their structural and electrochemical properties. High-resolution electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy results show that crystalline Ag nanoclusters are well dispersed within an amorphous RuO2. The Ag nanocluster-incorporated RuO2 electrodes show much higher capacitance of similar to 1306.0 F/cm(3) at 200 mV/s with superb high-rate performance compared to RuO2-only electrodes. The improved capacitance is explained in terms of the presence of dispersed Ag nanoclusters embedded within the amorphous RuO2 matrix having good electrical conductivity. (C) 2008 The Electrochemical Society.