An efficient, cheap and safe process for the solvothermal synthesis of ruthenium nanocatalysts has been developed: it involves the innovative use of a microwave (MW) applicator for the in situ activation of the reaction in a stirred glass vessel without resorting to an oven. The synthesis was carried out by direct MW irradiation of an alcohol or glycol solution of the metal precursor RuCl(3)nH(2)O, in the presence of PVP (poly-N-vinyl-2-pyrrolidone) as stabilizing agent and eventually of gamma-Al2O3 as support. The addition of PVP appears not to be necessary for the in situ preparation of the supported systems. The synthesized nanocatalysts were characterized by UV-Vis, TEM and XPS measurements: colloidal and supported nanoparticles with an average diameter about 2 nm and a narrow distribution of sizes were obtained. The supported systems showed interesting performances in the selective hydrogenation of phenol to cyclohexanone. (C) 2008 Elsevier B.V. All rights reserved.