High surface area MoO3/MgO (200-300 m(2) g(-1)) catalysts were prepared and rested in hydrodesulphurization of benzothiophene, The new slurry impregnation method was used that overcome the problem of chemical and textural instability of MgO support in aqueous impregnation solution of ammonium heptamolybdate. Molybdena was deposited by the reaction of MgO with the slurry of MoO3 in aqueous methanol or ethanol at room temperature. Small amount of water added to alcohol (4 and 6% for methanol and ethanol, respectively) did not hurt texture of MgO and accelerated the impregnation reaction. The method is a special case of equilibrium adsorption impregnation. The maximum (saturated) amount of MoO3 deposited on MgO of surface area of about 250 m(2) g(-1) was about 22 wt.% MoO3. However, hydrodesulphurization activity increased linearly only up to the loading of 15-20 wt.% MoO3. XRD confirmed that molybdena is deposited in finely dispersed form. Hydrodesulphurization activity of the best MoO3/MgO samples was the same as activity of the reference industrial MoO3/Al2O3 catalyst.