Understanding of the distribution of cavitational activity helps in achieving efficient design and scale up of sonochemical reactors. The experimental investigation of the mapping of cavitational activity has been performed in the present work in a large scale sonochemical reactor operating at 40 kHz with a capacity of 72 L The reactor is a multiple transducer rectangular flow cell type reactor operating at variable power dissipation levels with maximum rating of 2400 W. Two chemical dosimeters have been used for the mapping studies as potassium iodide and dichlorvos degradation for the quantification of cavitational activity. The calorimetric power measurement has also been performed to quantify the actual power dissipation in the liquid medium. Effect of input power on the cavitational activity has been investigated at different locations in the ultrasonic flow cell. The obtained results have established that there is good agreement between the two chemical dosimeters. Also the cavitational activity distribution was fairly uniform as compared to other conventional designs based on the use of single transducer. It has been also confirmed that the novel method based on dichlorvos degradation adapted in the present work can be used as one of the mapping techniques to establish better correspondence with the wastewater treatment applications due to similarity in the controlling mechanisms. Overall, the new design presented in the work gives uniform distribution of the cavitational activity to a greater extent and can be a useful design for commercial scale installations. (C) 2014 Elsevier B.V. All rights reserved.