The synthesis of suspensions of nanoparticles of molybdenum and aluminum oxides from inverted microemulsions with a dispersion medium composed of paraffin and aromatic hydrocarbons has been studied. The thermal decomposition of the precursors of catalyst components (water-soluble salts of Mo and Al) has been examined by thermogravimetric analysis and differential scanning calorimetry. The nature of the effect of the parameters of inverted microemulsions and conditions of their treatment on the particle size in the target Al- and Mo-containing suspensions has been revealed. The dispersity and composition of the resulting suspensions of nanosized particles have been analyzed.