The sonolysis of Basic Blue 41 dye in aqueous solution was performed at 35 kHz using ultrasonic power of 160W and aqueous temperature of 25 + 1 degrees C within 180 min. The TiO2 nanoparticles were used as a catalyst to assist the sonication process. The effect of experimental parameters such as pH, H2O2 concentration and initial dye concentration on the reaction were investigated. It was recognized that in lower pH values the dye removal rate decreased. However, dye removal increased via increase in H2O2 concentration and lowering the initial dye concentration. All intermediate compounds were detected by integrated gas chromatography-mass spectrometry (GC/MS) and also ion chromatograph (IC). During the decolorization, all nitrogen atoms and aromatic groups of Basic Blue 41 were converted to urea, nitrate, formic acid, acetic acid and oxalic acid, etc. Kinetic studies revealed that the degradation process followed pseudo-first order mechanism with the correlation coefficient (R-2) of 0.9918 under experimental conditions. The results showed that power ultrasound can be regarded as an appropriate tool for degradation of azo dyes to non-toxic end products. (C) 2007 Elsevier B.V. All rights reserved.