The copper(I) and copper(II) chloride-catalyzed radical chain oxidation of styrene with oxygen in acetonitrile was studied. The complex reaction of free-radical formation was described by the equation of the initiation rate V-i = k'[O-2](1.2)[PP](0.6)[Cu](0)[St](1) or, in an oxygen atmosphere, approximately V-i = k(i)[PP](1)[Cu](0)[St](1), where PP is styrene polyperoxide, St is styrene, and k(i) = 6.9 x 10(6)exp(-76 U mol(-1)/RT) 1/(mol s) (328-343 K). A formal kinetic scheme of the initiation mechanism was proposed. The scheme explains the combination of the dependence of V-i on the oxygen concentration with the involvement of the oxidation product polyperoxide in the initiation.