The paper gives results of experimental measurements of NO, N2, and other nitrogenous species in the postflame games of rich (phi = 2.17) premixed laminar CO/Ar/O2 (trace H2) flames, with fuel nitrogen as NO, C2N2, and NH3 and fuel sulfur as SO2, which allowed the nitrogen balance to be closed to within 7%. In the absence of hydrocarbons, and with only a trace of hydrogen, NO decayed homogeneously to form N2 at high temperatures, and the fate of nitrogen was independent of the type of fuel nitrogen species. The effect of fuel sulfur was to decrease postflame NO levels and increase N2 more rapidly. The observed decay in NO and formation of N2 were consistent with detailed kinetic calculations employing only the reverse Zeldovich mechanisms to form N and N2. There was no evidence of other N2 formation mechanisms being important for these hydrogen-poor flames, at either high or low temperatures. Calculations also showed that the most plausible effect of SO2 in the mixture was to increase the steady-state N-atom concentration through direct interactions between N, NO, S, and SO. (Copyright (c) 1983 by The Combustion Institute.)