The reduction of NO by black liquor char and activated carbon was studied at atmospheric pressure in a fixed bed reactor at temperatures between 450 and 650 degrees C. Black liquor char has a high Na to fixed C ratio (2.7), and the Na is well dispersed within the carbon matrix. The reduction of NO by both materials was confirmed to be of first order with respect to NO. The reaction rate constant, based on total surface area, for black liquor char was over 3 orders of magnitude higher than that for activated carbon which is consistent with the role of Na in catalyzing the NO reduction reaction. In the temperature range studied, N-2 and CO2 were the major reaction products for the reaction by black liquor char. In the presence of CO, the rate of NO reduction by black liquor char was enhanced by CO over the temperature range studied by a factor of 2.5 with 4% CO. The consumption of carbon was reduced to zero and the black liquor char provided a catalytic surface for NO reduction by CO. The activation energies of NO reduction by black liquor char both in the absence and presence of CO and by activated carbon were all within the range 67-73 kJ/mol.