Studies were conducted which used the ozone/hydrogen peroxide (O-3/H2O2) advanced oxidation process to pretreat three classes of compounds prior to aerobic biological treatment. The study compounds included ethylene oxide/ propylene oxide (EO/PO) block copolymers, polypropylene glycols (PPGs), linear secondary alcoholethoxylates (LSAEs), and alkylphenolethoxylates (APEs). After preoxidation with ozone and hydrogen peroxide (added at their stoichiometric ratio), 300 mg/L as COD samples were bioassayed in aerobic batch bioassays with a mixed liquor suspended solids concentration of 1500 mg/L. It was found that unoxidized polypropylated compounds (EO/PO block copolymers and PPGs) and LSAEs tended to be biorecalcitrant, while alkylphenolethoxylates (APEs) were partially biodegradable, increasing oxidant dosages (i.e., ozone plus stoichiometric hydrogen peroxide) consistently increased both the rate and extent of biodegradation of these compounds with the exception of NP(EO)(5), which initially decreased in biodegradability upon oxidation. Oxidant dosages required to enhance biodegradability varied significantly between and within classes of surfactant. for example, the average oxidant dosages required to reach an 85% DOC removal in the batch bioassays were 0.3 mg O-3/mg compound (plus H2O2) for LSAEs, 1.0 mg/mg for EO/ PO and PPGs, and 5.0 mg/mg for APEs, respectively.