Usefulness of the concept of bi- or multifunctional catalysis in the catalyst design for the reduction of dilute nitrogen oxides by hydrocarbons in the presence of excess oxygen (so-called HC-SCR) is demonstrated. First, it is shown that the complex reaction of HC-SCR can be divided into (i) the oxidation of NO to NO2 and (ii) the subsequent reactions between NO2 and hydrocarbons. Further, two examples, where significant improvement of catalytic performance was obtained, based on the idea of bifunctional catalysis are presented : (a) NO-C3H6-O-2 catalyzed by mechanical mixtures of Mn2O3 and M-ZSM-5 (metal loaded ZSM-5), and (b) NO-CH4-O-2 by Pd/H-ZSM-5 (Pd loaded H-ZSM-5).