Electrokinetics alone (EK) and ultrasonically enhanced electrokinetics (EK-US) tests were studied to compare and examine the combining effects of these two methods on the removal of the three persistent organic pollutants (POPs): hexachlorobenzene (HCB), phenanthrene (PHE) and fluoranthene (FLU) from kaolin. Two pair tests were conducted into two experiments with different initial low (100 mg/kg) and high (500 mg/kg) contaminant concentrations. Results from the experiments show that. generally, EX-US tests have higher electroosmotic flow, higher current and better performance than EK alone tests. However, ultrasonic enhancement can increase the removal rate only up to about 10% more. Among the three POPs, HCB is the most difficult to treat because of its very stable Structure while the other two PAHs are easier to remove. (C) 2008 Elsevier Ltd. All rights reserved.