Highly dispersed Ni(Co)-Mo-S sulfides were prepared by simple room temperature solution reactions using nickel or cobalt salts and thiomolybdate precursors in the presence of nonionic surfactants. The products were characterized by X-ray powder diffraction, specific surface area measurements, and scanning and transmission electron microscopy. The evolution front amorphous pre-catalysts to highly dispersed sulfide catalysts during the activation step was studied by thermal analysis. Extended X-ray absorption fine structure measurements were carried out to elucidate the chemical environment of the transition metals in the precursors and the sulfided catalysts. The specific catalytic activities of the Ni(Co)-Mo-S systems in the hydrodesulfurization of thiophene and 4,6-DMDBT were LIP to Six times higher than those of commercial alumina-supported systems. (c) 2005 Elsevier Inc. All rights reserved.