This work evaluates the effect of low frequency ultrasonic irradiation on the sonoelectro-Fenton (SEF) oxidation process in an acid aqueous medium. Ultrasonic irradiation significantly increases the H2O2 production rate and reduces the time needed to reach the maximum H2O2 concentration. In addition, ultrasonic irradiation has a considerable effect on the degradation of the cationic red X-GRL in the SEF process. A pseudo-first-order model was used to simulate the experimental results, and this revealed that the decolorization rate increased with the ultrasonic power in the SEF process. Furthermore, both TOC removal efficiency and mineralization current efficiency were greatly promoted in the SEF process compared with the electro-Fenton (EF) process. These results prove that the SEF process is a promising technology in terms of colored wastewater treatment. (C) 2010 Elsevier B.V. All rights reserved.