Temkin’s theory of rates of catalytic reactions on non-uniform surfaces is extended to the MoO3-catalyzed oxidation of ethanol to acetaldehyde. Two types of sites are assumed to be present, an oxygen atom site that can be modeled with uniform properties and a metal atom site characterized by non-uniform properties both for ethanol chemisorption to an ethoxide intermediate and the conversion of this intermediate to acetaldehyde. The rate-limiting step is the cleavage of a C-H bond in the absorbed ethoxide intermediate. Non-uniform surface kinetics leads to a kinetic rate expression of the form v = kP(C2H5OH)(1-m)P(O2)((1-m)/4)P-H2O(-(1-m)/2). Such a rate expression, with m = 0.14, is shown to provide a good fit to kinetic data for the selective oxidation of ethanol on a silica supported molybdenum oxide catalyst.