The aim of the study was to investigate decolorization of Rhodamine B (RB) in aqueous solution using ultrasonic degradation. The results showed that decolorization follows pseudo-first-order reaction kinetics. The apparent reaction rate constant (k(ap)) was found to increase with decreasing pH and decreases with increasing initial RB concentration. Power density was very important parameter and increasing it causes a considerable increase of removal efficiency. UV-vis spectral changes of RB indicate that in the sonolysis of RB, the cleavage of aromatic chromophore ring structure and the N-deethylation take place, but decomposition of aromatic structure is predominant. (c) 2007 Elsevier B.V. All rights reserved.