Emission regulations for unburned hydrocarbons, nitrogen oxides and particulates are becoming more stringent throughout the world. Nitrogen oxides include NO, NO2 and N2O. Transportation (mobile source) and fuel combustion (stationary source) are the main sources of nitrogen oxide emissions [1]. This review will update the commercial catalytic applications for abating nitrogen compounds (including nitrogen oxides) and will summarize the status of the following technologies applied to stationary source emissions: (1) selective catalytic reduction of NOx using ammonia (SCR); (2) non-selective catalytic reduction of NO, (NSCR); (3) nitrous oxide (N2O) decomposition; and (4) ammonia (NH3) decomposition. The major sources of NO, from stationary sources are power generation, stationary engines, industrial boilers, process heaters and gas turbines [2]. SCR is usually applied to all these sources and NSCR is applied mainly to the stationary engines. N2O decomposition is used mainly in the chemical industry associated with nylon intermediate manufacture. NH3 decomposition is a fairly new application and can be applied to SCR to decompose NH3 emissions from industrial operations.