The effects of operational parameters upon the hydroxyl radical generation of sonochemical reactors are critical to optimize this technology for wastewater treatment purposes. Salicylic acid dosimetry, due to its chemical and physical properties, is a very adequate method to characterize a sonochemical reactor by indirect determination of the (OH)-O-center dot radicals generated in the cavitating process. The degradation products, 2,5-dihydroxybenzoic acid (2,5-DHB) and 2,3-dihydroxybenzoic acid (2,3-DHB). are specific and easily determined with HPLC methods. The most significant parameters were determined by designing a 2(5) factorial set of experiments and applying some statistical tools to the results obtained with the dosimeter. When operating within a limited range (typical range of standard sonochemical reactors) the statistical tools showed that only the dosimeter concentration and the reactor geometry were mathematically significant in the process. (C) 2009 Elsevier B.V. All rights reserved.