A model experiment shows that phenylacetio acid may conveniently be formed from the alcoholic alkaline hydrolysis of α,β,β-trichloroethylbenzene at 170℃ under a pressure of 20 kg/cma with high yield, ca. 90%.In order to search a practical source of the latter, styrene is subjected to chlorination in the presence of 0.1% benzoyl peroxide at 100~110℃, which yields a mixture of thirteen constituents (Fig. 1 and Table 1).It is found that inspite of its highly complex composition, the crude chlorination product gives relatively simple acidic components, i.e., phenylacetio acid, a-ethoxyphenylacetic acid and benzoic acid, after hydrolysis under the samo conditions given above, with yields based upon styrene of 56~63%,ca. 7% and ca. 0.6%,respectively.