Sonocatalytic degradation of Rhodamine B was investigated using titanium dioxide (TiO2) powder and titanium dioxide nanotubes (TiO2 NTs) which were synthesized using sol-gel and hydrothermal method, respectively. Structural and crystalline information for both types of catalyst were characterized using transmission electron microscope (TEM), X-ray diffractometer (XRD) and surface analyzer. Remarkable improvement in the sonocatalytic activity of TiO2 NTs was achieved due to their high specific surface area and unique pore system. Effects of reaction parameters such as pH (2-10), ultrasonic power (20-100W), ultrasonic frequency (35 kHz and 130 kHz) and the presence of air flow (1 L/min) were also investigated. Under optimum conditions, i.e., with 8 millimolar (mM) of hydrogen peroxide (H2O2) and 1 L/min of air flow at neutral pH, 85% degradation of 50 mg/L Rhodamine B could be achieved in 120 min by the system with 2 g/L of TiO2 NTs. The sonocatalytic process was observed to behave according to a pseudo-first-order kinetics under different experimental conditions. In conclusion, sonocatalytic degradation in the presence of TiO2 NTs shows a great potential for the efficient treatment of organic dyes in wastewater. (C) 2011 Elsevier B.V. All rights reserved.