Pulse radiolysis was used to study the kinetics of the reactions of CH₃C(O)CH₂O₂ radicals with NO and NO₂ at 295 K. By monitoring the rate of formation and decay of NO₂ using its absorption at 400 and 450 nm the rate constants k(CH₃C(O)CH₂O₂ + NO) = (8 ± 2) × 10^-12 and k(CH₃C(O)CH₂O₂ + NO₂) = (6.4 ± 0.6) × 10^-12 cm³ molecule^-1 s^-1 were determined. Long path length Fourier transform infrared spectrometers were used to investigate the IR spectrum and thermal stability of the peroxynitrate, CH₃C(O)CH₂O₂NO₂. A value of k_-6 ≈ 3 s^-1 was determined for the rate of thermal decomposition of CH₃C(O)CH₂O₂NO₂ in 700 torr total pressure of O₂ diluent at 295 K. When combined with lower temperature studies (250-275 K) a decomposition rate of k_-6 = 1.9 × 10¹⁶ exp (- 10830/T) s^-1 is determined. Density functional theory was used to calculate the IR spectrum of CH₃C(O)CH₂O₂NO₂. Finally, the rate constants for reactions of the CH₃C(O)CH₂ radical with NO and NO₂ were determined to be k(CH₃C(O)CH₂ + NO) = (2.6 ± 0.3) × 10^-11 and k(CH₃C(O)CH₂ + NO₂) = (1.6 ± 0.4) × 10^-11 cm³ molecule^-1 s^-1. The results are discussed in the context of the atmospheric chemistry of acetone and the long range atmospheric transport of NO_x.