The relative yields of CH3NO2, CH3ONO, and CH3ONO2 have been measured at five temperatures between 323 and 455 K above 300 torr of pressure. Kinetic modelling of the observed CH3NO2/(CH3ONO + CH3ONO2) and CH3ONO/CH3ONO2 ratios from this study and that of Phillips and Shaw (Ref. 5), with and without added NO, led to the rate constant for CH3 + NO2 → CH3NO2 (1), k1 = 6.0x1012 cc/mol-sec, and for CH3O + NO2 → CH3ONO2 (4), k4 = 7.5x1012 cc/mol-sec. The results of the modelling also indicate that the oxidation of CH3NO by NO2 accounts for a large fraction of CH3NO2 formed in the NO-added mixtures. The rate constant for this reaction is estimated to be k25 ≃ 1.3×109 e(-10, 000/RT) cc/mol-sec. Combination of k1 with the equilibrium constant for reaction (1) gives rise to the rate constant for the decomposition of CH3NO2, k−1 = 1.3x1016 e(-60, 050/RT) sec−1.