A method of reducing NO.sub.X within a gas stream includes the step of placing a NO.sub.X reducing catalyst within a flue gas stream. The NO.sub.X reducing catalyst activity is enhanced by applying a separate activating source that significantly improves removal of NO.sub.X from the flue gas stream. The NO.sub.X reducing catalyst may be a stationary NO.sub.X reducing catalyst structure positioned in the flue gas stream. Alternately, the NO.sub.X reducing catalyst may be injected into the flue gas stream as a NO.sub.X reducing catalyst powder. The NO.sub.X reducing catalyst powder may be subsequently gathered in a particulate collection device. The NO.sub.X reducing catalyst may be further activated in the particulate collection device. The operation of separately activating the NO.sub.X reducing catalyst may be implemented by applying electromagnetic energy to the NO.sub.X reducing catalyst, by applying an electric field to the NO.sub.X reducing catalyst, by applying electric current through the NO.sub.X reducing catalyst, or by applying a magnetic field to the NO.sub.X reducing catalyst.