Bimetallic gamma-Al2O3-supported COMO and NiMo sulfide catalysts were prepared using ammonium thiomolybdate (ATM), tetramethylammonium thiomolybdate (TMATM), tetrabutylammonium thiomolybdate (TBATM), cetyltrimethylammonium thiomolybdate (CTMATM) as precursors for MoS2. The CO chemisorption study showed better dispersion of MoS2 on gamma-Al2O3 support in the catalysts prepared from the thiosalts precursor than the catalysts obtained from the oxides precursor. Among the catalysts derived from tetraalkylammonium thiomolybdates, Co(Ni)Mo/gamma-Al2O3 catalysts derived from CTMATM precursor showed higher CO uptake. The presence of molybdenum carbide phase in the Co(Ni)MoS2 catalysts formed from the tetraalkylammonium thiomolybdates is evidenced by NEWS study. DRIFT spectra showed lesser amount of partially sulfided molybdenum species in thiosalts-derived catalysts compared to those catalysts prepared by the conventional oxide precursors. The HDN and HDS activities of Co(Ni)Mo/gamma-Al2O3 sulfide catalysts with coker light gas oil (KLGO) feed at temperature, pressure and LHSV of 350 degrees C, 8.8 MPa and 1.5 h(-1) were studied. The activity of thiosalts-derived catalysts is significantly higher than the respective oxides precursor catalysts. The presence of carbo-sulfide phases promotes the HDN and HDS activities of tetraalkylammonium thiomolybdates derived NiMo and COMO catalysts. In both NiMo and COMO series, catalyst prepared by in situ decomposition CTMATM showed a maximum HDN and HDS activities as result of better dispersion of active phase on the support via microemulsion. (C) 2008 Elsevier B.V. All rights reserved.