A new method for synthesis of supported metal catalysts is described. The steps in this method are : (1) production of nanometer diameter metal clusters by gas aggregation, (2) capture and stabilization of the clusters as a colloidal suspension in an organic solvent, (3) adsorption of the clusters onto a high-surface-area support, (4) removal of the support particles from the solvent, and finally (5) oxidation/reduction treatment to remove residual solvent and surfactant. Ag/SiO2 catalysts with controlled Ag cluster diameters of 2.4, 4.4, 5.2, 8, and 11 nm were produced by this method. The size distribution of the clusters as characterized by transmission electron microscopy is essentially constant from step 1 to step 5.