There is provided a process for the treatment of exhaust gas, which process uses a specially prepared catalyst composition, for the selective catalytic reduction of NO.sub.x contained in the exhaust gas. An embodiment of the process of this invention comprises a catalytic stage to selectively catalytically reduce NO.sub.x over a catalyst composition comprising an intermediate pore size zeolite catalyst that has been treated with a water soluble iron salt or salt precursor in a way effective to maximize iron dispersion. The intermediate pore size zeolite of this invention preferably has a silica:alumina molar ratio of between about 20 and about 1000. The catalyst of this invention typically comprises a silica, titania, or zirconia binder, preferably a binder including a high molecular weight, hydroxyl functional silicone resin. The catalyst of this invention is preferably formed, e.g., extruded, and then simultaneously calcined and hydrothermally treated.