The adsorption and reactions of benzenethiol have been analyzed on the Ni(111) surface using TPD, XPS, LEED and HREELS. At 110 K, benzenethiol adsorbs on the surface through the sulfur atom. The vibrational data indicate that the S-H bond in benzenethiol breaks upon adsorption at 110 K for all exposures. The primary surface intermediate observed for high coverages of benzenethiol at 190 K is phenyl thiolate. HREELS results indicate that the aromatic ring in phenyl thiolate is neither parallel nor perpendicular to the surface, but tilted. For low coverages of benzenethiol, decomposition of the molecule to gaseous hydrogen, atomic sulfur, and carbon is the favored reaction pathway, while benzene formation is the dominant reaction for higher coverages. Two pathways are observed for the desorption of the benzene product. At intermediate coverages a desorption-limited process occurs near 400 K, while at high coverages benzene desorption is limited by hydrogenolysis of phenyl thiolate at 263 K. Above 300 K, a stable aromatic hydrocarbon intermediate, most Likely a phenyl fragment, is observed on the sulfur-covered Ni(111) surface. This intermediate stays almost parallel to the surface at 450 K. Annealing benzenethiol overlayers on the Ni(111) surface to 800 K results in a complex (root 39 x root 39)-S LEED pattern possibly as the result of the reconstruction of the top Ni layer over a broad coverage range.