CH3ONO was pyrolyzed in two different temperature regimes in order to determine the kinetics of the CH3O decomposition reaction. A static reactor operating between 550 and 770 K was used for the first set of experiments, with analysis of products (CO, CH2O, and CH3OH) by FTIR absorption. In the second set of experiments, a shock tube operating in the range 1000-1600 K was employed and the CO product was measured by resonance absorption of the output of a stabilized CW CO laser. Kinetic modeling of CO product yields over the full range of temperature (550-1660 K) allowed us to obtain for the first time the rate constant for the decomposition of CH3O: CH3O + M → H + CH2O + M (8), k8 = (5.45 ± 0.63) × 1013 exp(-6794 ± 102/T) cm3/(mol·s), where M = Ar or He, and the error limits represent only the internal consistency of the modeled values. Theoretical implications of this result are discussed.