A two-center Lennard-Jones plus point quadrupole (2CLJQ) effective pair potential model for nitrogen that had been shown in the past to be capable of fitting simultaneously thermodynamic and structural properties of the solid and the liquid, and the second virial coefficient of the gas, is tested for vapor-liquid equilibrium (VLE) in this work. Monte Carlo simulations in the Gibbs ensemble were carried out in order to obtain VLE data for pure nitrogen, the binary systems nitrogen + methane, nitrogen + ethane, and nitrogen + carbon dioxide, and the ternary system nitrogen + methane + ethane. Previously validated effective pair potential models were used for methane, ethane, and carbon dioxide. No binary adjustable parameters were needed to compute the unlike-pair Lennard-Jones interactions in the binary and ternary systems. Simulation results were found to be in relatively good agreement with the experimental data available for pressure and phase composition of the binary systems nitrogen + methane at 130, 150 and 170 K, nitrogen + ethane at 260, 270 and 280 K, and nitrogen + carbon dioxide at 220 and 240 K, and for the vapor-liquid phase compositions of the ternary system nitrogen + methane + ethane at 50.7 and 76 bar at 260 K. (C) 2003 Elsevier Science B.V. All rights reserved.