Effluent from the Pasakoy Wastewater Treatment Plant was oxidized by using O3 and O3/H2O2. DOC, COD, UV254, total coliform, dissolved ozone and some endocrine disrupting compounds were monitored during oxidation. Results showed that O3 provided superior disinfection, however, lower reductions in DOC, COD and endocrine disrupting compounds were exhibited compared to O3/H2O2. The highest removal efficiency of DOC, COD and endocrine disrupting compounds were achieved at 0.5 molar ratio of O3/H2O2. The benefit of H2O2 addition for advanced oxidation reduced significantly when the mole ratio was increased to 2. Therefore, the mole ratio of H2O2 to O3 is a critical parameter for the design of wastewater oxidation by O3/H2O2.