The effect of a reduction promoter, platinum, on the oxidation of a cobalt catalyst was studied. An induction period was observed for the unpromoted catalyst which was absent for the Pt-promoted catalyst. The rate of oxidation was similar for both the Pt-promoted and unpromoted catalyst in the range of degrees of reduction between 50 and 10%. The rate of oxidation of the remainder of metallic cobalt was, however, faster for the platinum promoted catalyst.