Oil-soluble molybdenum precursors such as naphthenates are used as additives for the hydroconversion of heavy petroleum residues. Under the conditions of hydroconversion processes, molybdenum naphthenate yields molybdenum sulfide and, simultaneously, a carbonaceous phase is produced. The complex solid resulting from the interaction of these phases exhibits a high surface area, outstanding catalytic activity and stability. These properties are attributed to the presence of the carbon phase. The present work consists in a systematic investigation of the influence of compositional and physical parameters upon the composition, surface area and catalytic properties of dispersed molybdenum sulfides generated in a pure synthetic medium representative of crude oil, A factorial design, based upon previous results concerning the nature of the catalytic precursor, has been elaborated. The following parameters have been considered in the present study: nature of the solvent (aromatic or aliphatic), nature of the sulfiding reagent, temperature, concentration of the precursor, residence time. It has been established that the nature of the solvent (aromatic or aliphatic) and the sulfiding reactant had a significant influence on the properties. An interactive effect between the nature of the sulfiding reagent and the concentration of the precursor has been evidenced.