The activities of sulfided Mo/C, W/C, Co/C, Ni/C, Co-Mo/C, and Ni-W/C catalysts for thiophene hydrodesulfurization and butene hydrogenation were studied using a flow microreactor operating at atmospheric pressure. The following parameters were varied: type of carbon support, carbon pretreatment, catalyst preparation method, and content of active material. The results are compared with those obtained for series of sulfided Mo/¿-Al2O3, W/¿-Al2O3, Mo/SiO2, and W/SiO2. Some samples, viz., Mo/C, Co/C, and Co-Mo/C, were also studied by X-ray photoelectron spectroscopy (XPS). The carbon-supported catalysts demonstrated outstanding performance for thiophene hydrodesulfurization. XPS analysis showed the presence of low-valence-state sulfur, e.g., S- or (S-S)2-, in Mo/C and Co/C catalysts with low molybdenum or cobalt content. These sulfurspecies are supposedly connected with the catalytic activity for hydrodesulfurization. Co/C and Ni/C were found to have a hydrodesulfurization activity which was higher (Co) or the same (Ni) as that measured for Mo/C or W/C. Therefore Co (Ni) ions in Co (Ni)-Mo (W)/C catalysts are considered as promoters for the MoS2 (WS2) phase (low Co/Mo or Ni/W ratios) or as additional active species.