The N(S-4(3/2)) + NO (k(1)) and N(S-4(3/2)) + NO2 (k(2)) gas-phase reactions, relevant to upper-atmospheric NOx chemistry, were studied using a discharge flow tube reactor with atomic resonance fluorescence detection of O(P-3) atoms. Reaction rate coefficients were measured over the temperature range 216-344 K to be k(1)(T) = (2.61 +/- 0.19) x 10(-11) exp((86 +/- 21)/T) and k(2)(T) = (2.41 +/- 0.62) x 10(-12) exp((442 +/- 64)/T) cm(3) molecule(-1) s(-1). The O(P-3) yield in the NO2 reaction was found to be 0.66 +/- 0.06. Our results are compared with previous studies and rate coefficient recommendations are provided.