Isobaric vapor-liquid equilibrium (VLE) data of the binary and ternary systems formed by the combination of acetone, methanol and methyl methacrylate, are determined at atmospheric pressure by means of an equilibrium still. The binary data have been correlated by means of the Wilson equation. The equilibrium results for the ternary system are also compared with the values predicted by this equation. It is found to be in very good agreement. A practical problem occurring in the case of distillation of the ternary mixtures is explained on the basis of the new results.