Gibbs ensemble Monte Carlo (GEMC) simulations are reported for the vapor-liquid phase coexistence of neon using an accurate ab initio pair potential (NE3) and also a quantum effective Wigner-Kirkwood potential (NE3-WK) based on the NE3 potential. It is noticed that the results from simulations for the thermodynamic properties of phase equilibria deviate from the experimental values (the simulated curve is outside the experimental temperature-density phase envelope). With an ab initio three-body potential of limited quality, the thermodynamic properties of phase equilibria are estimated in good agreement with experiment. It should be stressed that in contrast to most other work no empirical data are used in the present work. (C) 2004 Elsevier B.V. All rights reserved.