The Co, Mo and CoMo catalysts in different COMO ratios supported on SiO2, ZrO2, TiO2, Al2O3, active carbon and MgO were prepared. The catalysts were tested in the hydrodesulphurisation of benzothiophene. The order of activity of monometallic Mo catalysts was MoO3/ TiO2 > MoO3/C > MoO3/ZrO2 > MoO3/SiO2 > MoO3/Al2O3 > MoO3/MgO. The order of promotion of MoO3/support by Co addition was CoMo/MgO > CoMo/C > CoMo/Al2O3 > CoMo/TiO2 > COMO/ZrO2 > COMO/SiO2. The synergism in activity was accompanied with a decrease of hydrogenation/hydrogenolysis selectivity. Hydrogenolysis was promoted more than hydrogenation and thus less dihydrobenzothiophene was formed on COMO than on Co and Mo catalysts. The TPR patterns were measured, and the degree of reduction correlated with the activity of monometallic catalysts. The TPR patterns of COMO catalysts were similar to the patterns of Mo catalysts, and no correlation with magnitude of promotion was found. (C) 2007 Elsevier B.V. All rights reserved.