Hydrogen sulfide was observed by scanning tunneling microscopy to easily corrode a Au(111) surface, as suggested by an increase in surface roughness upon H2S exposure to the surface. However, this process could be tempered by moderating the concentration of H2S in the vapor above the gold. When corrosion was minimized, corroded regions were observed to exist predominantly at step edges. At a sufficiently low concentration of H2S, linear triple-row structures were observed. These are not the same as those observed when aqueous sulfide was reacted with a gold surface. A model that accounts for all the features of the adlayer structure is presented that involves a packing density of hydrosulfide groups of 28.5 Angstrom(2)/molecule, which is lower than that found in a root 3 x root 3 R30 overlayer (21.5 Angstrom(2)/molecule) found for long-chain alkanethiolate self-assembled monolayers on Au(111).