There have been relatively few studies that have used molybdenum sulfide single crystals as model HDS catalysts. MoS2(0001) single crystal surfaces are largely unreactive toward many organosulfur compounds but can be ion-bombarded to form chemically active surfaces with large densities of sulfur vacancies (coordinately unsaturated Mo sites). XPS and AES measurements confirm that sulfur is preferentially removed during ion-bombardment and that significant changes occur in the distribution of Mo oxidation states at the surface as a function of ion-bombardment time. Methanethiol adsorption studies were performed using TPD on ion-bombarded MoS2(0001) single-crystal surfaces. Methanethiol, methane, ethane, and ethylene were observed as decomposition products, which are thought to arise from methanethiolate and thioformaldehyde surface intermediates. Additionally, product selectivity varied as a function of cus Mo surface site densities.