Ru/SiO2 catalysts were prepared by sol-gel methods from Ru-3(CO)(12), Or [Ru3H(CO)(11)](-), Si(OMe)(4) (TMOS) and H2O, followed by thermal activation in helium up to 573 K and reduction with hydrogen. They were compared with Ru/SiO2 corresponding material prepared via sol-gel from RuCl3. The catalysts were characterized by FT-IR spectra, surface area, metal dispersion and activity tests in the Fischer-Tropsch reaction at atmospheric pressure and CO/H-2 1:1, in the 473-573 K temperature range. The use of ruthenium clusters as precursors afforded higher metal dispersions than RuCl3, as well as higher catalytic activities in the hydrogenation of CO (particularly in the absence of alkali or halogen ions retained in the gel structure). TEM investigations on the Ru/SiO2 material, prepared from Ru-3(CO)(12) by sol-gel, without promoters, showed the presence of very fine metal particles homogeneously embedded in the silica matrix, with dimensions ranging from 1 to 4 nm.