The self-reaction rate constants of the (CH3)(2)CHC(O)O-2 and (CH3)(3)CC(O)O-2 acylperoxy radicals were determined by flash photolysis from 275 to 363 K yielding: k((CH3)(2)CHC(O)O-2) = (9.15 +/-1.1) X 10(-13) exp[(821 +/- 39)K/T] and k((CH3)(3)CC(O)O-2) = (2.0 +/-0.5) X 10(-12) exp[(586 +/- 70)K/T] cm(3) molecule(-1) s(-1), corresponding to (1.44 +/- 0.11) X 10(-11) and (1.43 +/- 0.11) X 10(-11) cm(3) molecule(-1) s(-1) at 298 K, respectively (global uncertainty of approximate to 30%). These values are very close to that recommended for CH3C(O)O-2. In addition, the room temperature rate constants of the cross-reactions (CH3)(2)CHC(O)O-2 + (CH3)(2)CHO2 and (CH3)(3)CC(O)O-2 + (CH3)(3)CO2 were estimated at (1.0 +/- 0.5) X 10(-11) and (1.25 +/- 0.5) X 10(-11) cm(3) molecule(-1) s(-1), respectively, also similar to those of the CH3C(O)O-2 radical cross-reactions.