The N(4S3/2) + NO (k1) and N(4S3/2) + NO2 (k2) gas-phase reactions, relevant to upper-atmospheric NOx chemistry, were studied using a discharge flow tube reactor with atomic resonance fluorescence detection of O(3P) atoms. Reaction rate coefficients were measured over the temperature range 216–344 K to be k1(T) = (2.61 ± 0.19) × 10−11 exp((86 ± 21)/T) and k2(T) = (2.41 ± 0.62) × 10−12 exp((442 ± 64)/T) cm3 molecule−1 s−1. The O(3P) 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.