The hydrogen content and the reactivity Of MoS2/gammaAl2O3 catalyst and gammaAl2O3 support mechanical mixtures have been investigated using high pressure toluene hydrogenation, hydrogen temperature programmed desorption (H-2-TPD), and oxygen chemisorption. It has been found by H-2-TPD and confirmed by the oxygen chemisorption that, in the presence of a MoS2/gammaAl2O3 catalyst, the gammaAl2O3 support contains some hydrogen species. These species are therefore provided by spillover from the MoS2 phase which possesses the active sites able to dissociate molecular hydrogen. However, no cooperative effect of mechanical mixtures on toluene hydrogenation activities obtained in typical hydrotreating conditions, i.e., 6 MPa and 350-degrees-C, both in the presence and in the absence of a H2S partial pressure, has been found.