The hydrodesulfurization (HDS) of tetrahydrothiophene was studied over model catalysts prepared by deposition of Co and Mo thin films on a stainless-steel foil covered with graphite. There are three main findings: (1) the nominal turnover rate for the HDS reaction is approximately constant and independent of the Co to Mo ratio, (2) the main product was 1,3-butadiene for cobalt and 1,3-butadiene and 1-butene for molybdenum, and (3) the reaction is not poisoned by sulfur. The surfaces were characterized by Auger electron spectroscopy (AES) before and after reaction. The reactions were carried out under 2.6 kPa of tetrahydrothiophene and 100 kPa of H-2 at 613 K.