The Au/Pt/Rh trimetallic nanoparticles were successfully synthesized by a combination of a co-reduction and a self-organization method using poly(N-vinyl-2-pyrrolidone) (PVP) as a protecting reagent. The triple core/shell structure was suggested by HR-TEM, EF-TEM and FT-IR-CO for the trimetallic nanoparticles. The present trimetallic nanoparticles had much higher catalytic activity for hydrogenation than the corresponding monometallic and bimetallic nanoparticles. This high catalytic activity can be due to the sequential electronic effect between different atoms of a particle, which is supported by XPS data. (C) 2007 Elsevier B.V. All rights reserved.