Phase compositions of simultaneous chemical and phase equilibria are measured with a static apparatus for the multicomponent system of acetic acid, amyl alcohol, amyl acetate, and water at temperatures from 373.15 to 393.15 K. Various molar ratios of acetic acid to amyl alcohol of feed, ranging from 1:3 to 3:1, are employed in the experiments. An acidic cation-exchange resin, Amberlyst 39, is used to promote the esterification. In addition, vapor-liquid equilibrium data are also determined for the binary mixtures of acetic acid + amyl alcohol at 333.15 K and acetic acid + amyl acetate at 353.15-393.15 K. These new binary data are applied to determine the binary parameters of the NRTL model for the corresponding systems that are needed for prediction of the multicomponent systems. By accounting the dimerization of acetic acid in the vapor phase, the reliability of the binary parameters obtained from different types of equilibrium data is evaluated by comparing the results of equilibrium calculations with the experimental phase compositions of the esterification system.