This study examines (1) the production of a clean polycrystallinesurface, (2) oxygen adsorption as a function of room‐temperature exposure using ion scatteringspectroscopy (ISS), Auger electron spectroscopy(AES), and electron spectroscopy for chemical analysis (ESCA), and (3) CO adsorption. S and Cl are typical contaminants which modify the chemisorption properties of a Zr surface. However, they are difficult to detect using AES or ESCA but are readily observed using ISS. Sputtering a hot Zr surface provides an excellent method for producing a contaminant‐free surface. The adsorption of oxygen proceeds in a stepwise fashion by rapidly populating sites in the outermost surface layer, filling subsurface sites and then forming a multilayer oxide film even at room temperature and low O2 pressure (10− 6 Torr). CO adsorbs dissociatively on Zr at room temperature. An oxide overlayer is formed which contains no C. The C lies beneath the oxide layer in a chemisorbed or interstitial form. Heating converts this C into a carbidic form and causes segregation of surface oxygen into the bulk Zr.