Molecular simulation data were used to study the performance of equations o
f state (EoS) and combining rules usually employed in thermodynamic propert
y calculations. The Monte Carlo method and the Gibbs ensemble technique wer
e used for determining composition and densities of vapor and liquid phases
in equilibrium for binary mixtures of Lennard-Jones fluids. Simulation res
ults are compared to data in the literature and to those calculated by the
t-PR-LJ EoS. The use of adequate combining rules has been shown to be very
important for the satisfactory representation of molecular simulation data.