The formation of cavitation bubbles is the significant process for the sonochemical reactions. Pyrolysis in the cavitation bubbles and the radical-initiated reactions on the interfaces and in the bulk liquid are known to be the predominant decomposition pathways. Hydrophobic compounds, which are easily concentrated on the surface of the bubbles, are present in a higher concentration compared with in the bulk liquid. Such compounds are susceptible to the decomposition by the OH radical-initiated reaction on the interfaces between the cavitation bubbles and the bulk liquid, in addition to the pyrolytic reaction. In this work, various monocyclic aromatic compounds were irradiated by 200kHz ultrasound for 3 minutes and the relationship between their initial degradation rates and two hydrophobic parameters, LogP(water-octanol partition coefficient) and surface excess concentrations, was investigated. LogP values were found as the parameters to predict the sonolysis rates of hydrophobic compounds.