Herein, the ultrasonic degradation of trichloroethylene (TCE) and carbon tetrachloride (CT) are reported. The degradation rate for TCE increased by 27% with a decrease in the initial concentration of TCE from 10 to 1 mg L(-1), while the degradation rate of CT was not influenced significantly (<3%) at varying initial concentrations. The addition of t-BuOH, a hydroxyl radical scavenger, decreased the degradation rate of TCE to 22-33%. However, this addition did not affect the degradation rate of CT. Sonolysis of aqueous mixtures of TCE and CT indicated that the degradation rate of TCE was enhanced significantly in the presence of CT, while the degradation rate of CT was slightly inhibited in the presence of TCE. The enhancement of TCE degradation is attributed to both the increase of hydroxyl radical concentration by scavenging of CT for hydrogen atoms and the generation of chlorine-containing radicals such as CCl(3)(*), CCl(2)(*), Cl(*), and HClO from pyrolysis of CT during sonolysis of CT.