We report the first STM observations of the thermally induced dewetting of an iron oxide scale from an Fe(lll) surface. In addition, we report the influence of the presence of S at the metal/oxide interface on substrate topography. Room-temperature oxidation of S-free and (1 x 1)-S-covered Fe(lll) surfaces at oxygen partial pressures of 1 x 10(-7) to 5 x 10(-7) Torr resulted in the growth of oxide islands, with the only difference being the formation of larger islands in the latter case. Line shape analyses of the Fe(MW) peak indicated a similar growth mechanism in both cases, with the formation of Fe3O4 initially and Fe2O3 at higher exposures of Oz. Flash annealing of the oxide formed on the S-free and (1 x 1)-S-covered surfaces in ultrahigh vacuum (UHV) resulted in oxide dewetting, leaving larger oxide islands separated by S-free or S-covered Fe regions, respectively. The presence of S at the metal/oxide interface causes oxide dewetting to occur at lower temperatures than those on a S-free surface. In the case of the (1 x 1)-S-covered phase, flash annealing to similar to 720 K induces enhanced sulfur segregation apart from dewetting. When the S/Fe Auger intensity ratio is sufficiently large prior to oxidation (>1.3), flash annealing causes dewetting of the oxide scale, and the final S coverage induces the (2 root 3 x 1)R30 degrees faceting transformation. However, if the ratio is lower than similar to 1.3, the faceting transition is not observed upon annealing, although oxide dewetting and S segregation are noted. In other words, oxide dewetting is "decoupled" from faceting. The additional sulfur segregation to the metal/oxide interface at comparatively lower temperatures is an unexpected occurrence and occurs only if some interfacial sulfur is already present.