The ultrasonically enhanced oxidation of polyethylene surfaces by potassium and ammonium persulfates is described. The use of ultrasound allows significant levels of surface modification to be achieved using these oxidizing agents under mild conditions. Changes in the water contact angle and attenuated total reflection infra-red spectra were used to follow the changes in surface chemistry. Variation of conditions such as sonication time, sound intensity and reaction temperature allowed control over the extent and nature of the surface oxidation.