In the present study, the liquid-phase reductive deposition as a novel nanoparticle synthesis method has been investigated and its application to supported noble metal catalyst preparation was also focused. As a result, the maximum loading of Pt was around 20 wt% with keeping the particle size below 2 nm, by the present technique based on the liquid-phase reduction method. The selective reductive deposition is characteristically performed by the adsorption of metal ion or complexes on the surfaces and hereby the reduction. Namely, the initial adsorption of metal ions or complexes is the key point of this technique. Hence, key points of this method are: (1) precise control of the metal complex by adjusting solute conditions, such as composition and structure of metal complex, (2) storing of the suspension until the equilibrium composition and (3) aging suspension at controlled temperature. The most important is the first one, as the adsorption of specific metal complex results in the generation of precursor solid on the surfaces of the supporting materials. By this novel method, not only Pt but also Au nanoparticles supported on various carriers were successfully obtained. (C) 2008 Elsevier B.V. All rights reserved.