The oxidizability value of styrene epoxide as the ratio k (2)/ask (6), where k (2) and k (6) are the propagation and termination rate constants of the epoxide oxidation chain, respectively, was calculated from experimental data on the oxidation of neat styrene epoxide with oxygen in the presence of the initiator dicumyl peroxide in a quartz reactor of a manometric unit. Alternative calculations of the oxidizability value with the use of two procedures and two experimental setups yielded close values of k (2)/ask (6) = 0.333exp(-22.5 kJ mol(-1)/RT) and k (2)/ask (6) = 0.18exp(-22.1 kJ mol(-1)/RT)(l/(mol s))(1/2) (393-413 K), which characterize a quite high stability of styrene epoxide toward oxidation by peroxide radicals. With allowance for the new data, it was concluded that the radical mechanism is unfeasible under the conditions of the earlier-studied mild acid-catalyzed oxidation of styrene epoxide (333-348 K).