This research note describes the sulfur tolerance in hydrodesulfurization for a set of CoMo and NiMo catalysts on various supports. The activity decrease with increasing H2S concentration is diminished by supports with enhanced Bronsted acidity. The sulfur tolerance for NiMo catalysts increases in the order activated carbon < alumina < titania < amorphous silica-alumina. A direct interaction between Bronsted acid sites and the active sites is proposed. Complexing agents decrease the sulfur tolerance for a given support due to stacking of MoS2 slabs. Clearly, CoMo catalysts are less prone to sulfur poisoning than NiMo catalysts. NiMo is the preferred metal combination for desulfurization under sulfur-lean conditions. (C) 2003 Elsevier Science (USA). All rights reserved.