The research work conducted in our group concerning the study of the potassium-catalyzed NOx reduction by carbon materials is presented. The importance of the different variables affecting the NOx-carbon reactions is discussed, e.g. carbon porosity, coal rank, potassium loading, influence of the binder used, and effect of the gas composition. The catalyst loading is the main feature affecting the selectivity for NOx reduction against O-2 combustion. The NOx reduction without important combustion in O-2 occurs between 350 and 475 degrees C in the presence of the catalyst. The presence of H2O in the gas mixture enhances NOx reduction at low carbon conversions, but as the reaction proceeds, it decreases as the selectivity does. The presence of CO2 diminishes the activity and selectivity of the catalyst. SO2 completely inhibits the catalytic activity of potassium due to sulfate formation.