The high-temperature rate constants of the reactions NCN + NO and NCN + NO2 have been directly measured behind shock waves under pseudo-first-order conditions. NCN has been generated by the pyrolysis of cyanogen azide (NCN3) and quantitatively detected by sensitive difference amplification laser absorption spectroscopy at a wavelength of 329.1302 nm. The NCN3 decomposition initially yields electronically excited (NCN)-N-1 radicals, which are subsequently transformed to the triplet ground state by collision-induced intersystem crossing (CIISC). CIISC efficiencies were found to increase in the order of Ar < NO2 < NO as the collision gases. The rate constants of the NCN + NO/NO2 reactions can be expressed as k(NCN+NO)/(cm(3) mol(-1)s(-1)) = 1.9 x 10(12) exp[-26.3 (kJ/mol)/RT] (+/- 7% Delta E-a = 1.6 kJ/mol, 764 K < T < 1944 K) and k(NCN+NO2)/(cm(3) mol(-1)s(-1) = 4.7 x 10(12) exp[-38.0(kJ/mol)/RT] (+/- 19%, Delta E-a = +/- 3.8 kJ/mol, 704 K < T < 1659 K). In striking contrast to reported low-temperature measurements, which are dominated by recombination processes, both reaction rates show a positive temperature dependence and are independent of the total density (1.7 x 10(-6) mol/cm(3) < p < 7.6 x 10(-6) mol/cm(3)). For both reactions, the minima of the total rate constants occur at temperatures below 700 K, showing that, at combustion-relevant temperatures, the overall reactions are dominated by direct or indirect abstraction pathways according to NCN + NO -> CN + N2O and NCN + NO2 -> NCNO + NO.