The selective catalytic reduction (SCR) of NO by propane in the presence of excess oxygen was studied on a Co=ZrO2 catalyst. This system is present as active for the NO reduction to N-2. It was found that the addition of Co could improve the activity and selectivity of propane towards NOx reduction. The activity depends strongly on the space velocity (GHSV) when the system works with low oxygen concentration and it is independent of the space velocity when the system operates with excess oxygen. The water vapor present in the feed produces deactivation in the catalyst as well as in the support.