The kinetics and mechanism for the thermal oxidation of nitrosobenzene by nitrogen dioxide have been studied experimentally by pyrolysis/Fourier transform infrared spectrometry and computationally by hybrid density functional theory calculations. The experimental data measured in the temperature range 373-473 K gave rise to the bimolecular rate constant for the direct O-exchange reaction, C6H5NO + NO2 -C6H5NO2 + NO, k(1) = (9.62 +/- 0.35) x 10(10) exp[-(6500 +/-144)/7] cm(3) Mol(-1) s(-1), which can be satisfactorily accounted for by the transition-state theory with the energy barrier, E-1(0) = 10.0 +/- 0.3 kcal mol(-1) at 0 K.