This paper deals with author＇s systematic studies concerning the development of highly active zeolite-based hydrodesulfurization catalysts. The author and associates revealed that reduced MeY zeolites (Me degrees Y) are effective for the hydrodesulfurization of thiophene, in which both Bronsted acid site and metal particles on Me degrees Y act as the active site for the hydrodesulfurization. A general rule was, thus, derived that the combination of strong Bronsted acid site and highly dispersed metal particles with high hydrogenating ability of zeolites provide high catalytic activity for the hydrodesulfurization of organic sulfur compounds. On the basis of this rule, we developed Rh catalysts supported on USY zeolite as second generation highly active zeolite-based hydrodesulfurization catalysts, which is much more active than commercial CoMo/Al2O3 hydrodesulfurization catalyst.