This work considers the mechanistic features of sonochemical degradation of volatile (chlorobenzene) and nonvolatile (phenol) organic pollutants. The sonochemical degradation of pollutant occurs in two pathways: thermal pyrolysis and hydroxylation. By coupling experimental results to bubble dynamics model, we have tried to establish relative contribution of these pathways to degradation of two kinds of pollutants. It is revealed that degradation of volatile pollutants occurs primarily by thermal pyrolysis while hydroxylation is the predominant mechanism of degradation of nonvolatile pollutants. The simulation results also help explain some interesting trends observed in degradation with reaction parameters such as initial pollutant concentration and salt addition to solution. These parameters are found to influence both pathways of degradation that leads to enhancement in degradation. However, the extent of this influence on hydroxylation and pyrolysis pathways is diffirent for phenol and chlorobenzene. This is attributed to different partitioning behavior and solubility of the two pollutants. (c) 2008 American Institute of Chemical Engineers.