A pulse-radiolysis system was used to measure absolute rate constants for the reactions of CH3C(O)O-2 radicals with NO and NO2 at 295 K and 1000 mbar total pressure of SF6. When the rate of formation and decay of NO2 using its absorption at 400.5 and 452 nm were monitored, the rate constants k(CH3C(O)O-2 + NO) = (2.0 +/- 0.3) x 10(-11) and k(CH3C(O)O-2 + NO2) = (1.0 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1) were determined; Long path-length Fourier transform infrared spectrometers were used to study the rate-constant ratio K(CH3C(O)O-2 + NO)/k(CH3C(O)O-2 + NO2) in 6-700 Torr total pressure of N-2 diluent at 243-295 K. At 295 K in 700 Ton of N-2 diluent k(CH3C(O)O-2 + NO)/k(CH3C(O)O-2 + NO2) = 2.07 +/- 0.21. The results are:discussed in the context of the-atmospheric chemistry of acetylperoxy radicals.