The oxidation of cumene in the presence of a mixture of two initiators, azobisisobutyronitrile and benzoyl peroxide, revealed the antagonistic effect of their action. This phenomenon was explained using mathematical simulation of the process by means of analyzing kinetic schemes. It was shown that the antagonistic effect is a result of formation of alkoxyl radicals at the stage of combination of cumene peroxyl radicals and their further participation in cross-termination reactions with initiator radicals. The temperature dependence of the initiators' effect has been analyzed.