Perchloric acid in a tert-butanol solution with 10 vol % chlorobenzene exhibits an almost three orders of magnitude higher activity in comparison with para-toluenesulfonic acid (TSA) as a catalyst for the parallel styrene epoxide (SE) heterolysis and homolysis processes. There is a substantial difference between the reactions mediated by these catalysts: rate curves for the overall consumption in the presence of perchloric acid (SE heterolysis) yield straight lines in the log [SE]-time coordinates, but the first-order rate constant drops with an increase in [SE]. However, the oxygen uptake rate increases with [SE]. In the case of TSA, neither overall consumption nor oxidation rate depended on [SE] at [SE] > [TSA]; i.e., the reaction was zeroorder in SE.