The reactivity of thiophene (C4H4S) and ethanethiol (CH3CH2SH) has been studied with TDS on the MoS2(0001) surface. No catalytic activity was detected for thiophene adsorption on MoS2(0001); however, ethanethiol decomposed into ethylene and hydrogen sulfide on the same surface. Ethanethiol is hypothesized to dissociatively adsorb as a thioethoxy surface species, which undergoes hydride elimination to give ethylene. Hydrogen sulfide is formed via hydrogen combination with lattice or adsorbed sulfur. Ethanethiol is thought to adsorb at catalytically active defect sites on the MoS2 basal plane, which are most likely coordinately unsaturated Mo+(VI) cations. The proposed mechanism is analgous to those observed between thiols and molybdenum/cobalt/suIfur (Cp(2)Mo(2)Co(2)S(3)(CO)(4)) clusters. The difference in reactivity between the thiol and aromatic organosulfur compound on MoS2 is thought to occur because of the difference in the C-S bond strengths in thiophene and ethanethiol.