The large sonochemical reactor was developed by using 12 PZT transducers. The frequency was 500 kHz and the total effective electric power applied to transducers was 620 W. The sample and volume were aqueous solution of potassium iodide and 112 dm(3), respectively. The ultrasonic power dissipated into solutions was measured by a calorimetric method. The energy conversion efficiency from electricity to ultrasound was 70%. When the liquid height was from 400 to 435 mm, the l(3)(-) production rate has a maximum value. The l(3)(-) production rate increased with increasing ultrasonic power. In the case of high ultrasonic power, the l(3)(-) production rate for transducers located at the side wall was higher than that at the bottom wall. The sonochemical efficiency for a large sonochemical reactor operated at 500 kHz was close in value to those for laboratory scale reactors at 500 kHz. (C) 2007 Elsevier B.V. All rights reserved.