The rate coefficients of the reactions of NCO radicals with NO and NO2: (1) NCO + NO → products (293–836 K) and : (2) NCO + NO2 → products (294–774 K) were measured by means of laser photolysis and laser induced fluorescence technique in the indicated temperature ranges. NCO radicals were produced from the reaction of CN, from photodissociation of ICN or BrCN, with O2. The concentration of NCO was monitored with a dye laser set at 414.95 nm. We determined k1 = 1.73 × 10−5 T−2.01 exp(−470/T) cm3 molecule−1 s−1 that agrees with published results at room temperature and confirms the temperature dependence of an early report. A non‐Arrhenius negative temperature dependence of k2 was observed in this work that agrees satisfactorily with results for a shock tube18 near 1250 K. We obtained k2 = 6.4 × 10−10 T−0.646 exp(164/T) cm3 molecule−1 s−1 for 1250 K ≥ T ≥ 294 K by combining data of these two measurements. Our result at 294 K and the temperature dependence disagree with results of two previous investigations. © 1995 John Wiley & Sons, Inc.