Time-resolved near-infrared cavity ring-down spectroscopy was applied to the kinetics of the gas-phase reaction of CH3O2 with NO at 100 Torr total pressure and 298 K. After flash photolysis of the CH4/Cl-2/O-2/N, mixture at 355 nm or the CH3I/O-2/N-2 mixture at 266 nm, the CH3O2 absorption at 1.36 mu m was Monitored for the kinetic study. The reaction rate constants determined in two different radical sources are essentially the same and in agreement with the recently proposed values.