This work presents the effect of different sulfiding agents on Mo-W-Ni trimetallic catalysts, such as "NEBULN" catalysts. The materials were prepared by direct precipitation of ammonium molybdate, ammonium tungstate and nickel nitrate, generating a trimetallic precursor designated NH4-Ni-Mo0.5W0.5-O. Hydrogen sulfide (H2S), dimethyl disulfide (DMDS) and dimethyl sulfide (DMS) in a hydrogen atmosphere were used to sulfide the precursor at 400 degrees C for 2 h. The NEBH2S, NEBDMDS and NEBDMS catalysts obtained were evaluated in the hydrodesulphurization (HDS) reaction of dibenzothiophene (DBT). DMDS and DMS are less polluting agents than H2S, which is indeed a highly toxic compound. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, textural properties were measured using the BET and BJH methods. NEBH2S and NEBDMDS catalysts present similar catalytic activities for HDS, higher than NEBDMS. However, the latter catalyst was the most selective towards biphenyl (BF). NEBH2S and NEBDMDS catalysts were exposed twice to the HDS reaction, they presented an improvement in catalytic activity compared to the first catalytic test. (c) 2005 Elsevier B.V. All rights reserved.