The high-pressure phase equilibrium of the ternary system carbon dioxide + water + acetic acid was studied experimentally at temperatures between 313 and 353 K and pressures between about 6 and 16 MPa with an arrangement based on the continuous flow technique. The experimental results are reported and compared to calculations applying the Peng-Robinson equation of state with various mixing rules. The representation of the experimental data could be considerably improved by taking into account the dimerization of acetic acid. The binary interaction parameters were adjusted to experimental data for the vapor-liquid equilibrium of the binary sub systems. The combination of the Peng-Robinson equation of state with the mixing rule of Panagiotopoulos and Reid which takes dimerization into account results in reliable predictions for the high-pressure phase equilibrium of the ternary system. (C) 2004 Elsevier B.V. All rights reserved.