Palladium nanocubes (27, 48, and 63 nm) composed of (100) planes were successfully synthesized for use in oxygen electroreduction in 1-M NaOH electrolyte. The results (at -0.1 V vs. Ag/AgCl) of a rotating ring-disk electrode measurement showed that the specific activities of the 27-, 48-, and 63-nm Pd nanocubes were 3.05 x 10(-2), 3.41 x 10(-2), and 2.44 x 10(-2) mA cm(-2), respectively. 48 nm Pd nanocubes exhibited the higher activity than larger nanocubes and 9 nm Pd nanoparticles, where the specific activity of nanoparticles was 2.16 x 10(-2) mA cm(-2). Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.