In this article the use of ozone for the treatment of pentylacetate contaminated waters is evaluated. Pentylacetate has started to be used in the drycleaning process as a new solvent due to its economic benefits. However, in the technical literature experimental data involving pentylacetate ozonation has not yet been reported. This article presents experimental results on the effect ofpH on the rate ofpentyalcetate removal by ozonation of contaminated waters. At acid pH, pentylacetate is removed by a combination of single sparging and direct ozone reaction. As pH increases, the rate of pentylacetate removal also increases, showing the importance of free radical mechanism. The constant of indirect reaction rate for pentylacetate removal due to radicals is 2.6 x 10(9) M-1s-1.