The solid solubilities of the isomers o-, m-, and p-methoxyphenylacetic acid were measured in supercritical carbon dioxide at 308.2 K over a pressure range of 11-34 MPa. The results were correlated by the Peng-Robinson equation of state and the augmented van der Waals-density-dependent local composition equation. The data showed that solubility increased in the order of o-, p-, and m-methoxyphenylacetic acid, and the latter equation of state gave a much better correlation than the Peng-Robinson equation.