The chemisorption of 1-octanethiol [CH3(CH2)(6)CH2SH] from the vapor phase on the GaN(0001)-(1 x 1) surface has been studied using X-ray photoemission, ultraviolet photoemission, and X-ray-excited Auger electron spectroscopies. Quantitative analysis of relative peak intensities indicates that the molecule adsorbs via the thiol group with a saturation coverage of similar to0.28 monolayers and with the alkyl chain lying essentially parallel to the surface. Upon annealing, most of the alkyl C desorbs by similar to350 degreesC, but most of the S remains. Little or no indication of X-ray-induced damage in the adsorbed thiol layer is seen during data collection.