The adsorption and decomposition of methanol are examined on (1 × 1)Pt(110) and (2 × 1)Pt(110). It was found that (1 × 1)Pt(110) and (2 × 1)Pt(110) behave very differently even though they have a very similar surface structure. When methanol decomposes on (2 × 1)Pt(110) only CO and H2 are formed. However, when methanol decomposes on (1 × 1)Pt(110) the CO bonds break at low temperature to yield water, methane, hydrogen, and adsorbed carbon. Yet, all of the steps, kinks, and atoms of special coordination present on (1 × 1)Pt(110) are also present on (2 × 1)Pt(110). These results imply that the active site for CO bond scission in methanol consists of an ensemble of many atoms rather than a step, kink, or atom of special coordination. © 1990.