The oxidation of the endocrine disruptor, diethylstilbestrol (DES) in aqueous media by ultrasound is significantly enhanced by Fe(II) catalyst. The observed enhancement is likely the result of increased levels of hydroxyl radicals from the iron-promoted reduction of the hydrogen peroxide produced during ultrasonic irradiation. The degradation is effective over a range of concentrations and is consistent with pseudo first-order kinetics. Relatively high concentrations of hydrogen peroxide, ∼ 450 mM, are present in solution under our experimental conditions after 1 h of ultrasonic irradiation (665 kHz). The concentration of H2O2 in solution decreased with the addition of Fe(II) along with an increase in the degradation of DES. Hydrogen peroxide alone does not appreciably degrade DES. Our results demonstrate ultrasonic-induced degradation of DES can be accelerated with the addition of Fe(II). The combination of ultrasonic irradiation and Fe(II)-promoted conversion of H2O2 to hydroxyl radical may provide a valuable strategy for the treatment of organic pollutants. © 2005 Elsevier B.V. All rights reserved.