The ethylene (C2H4)-NN-dimethylformamide (DMF) binary system at 293.25, 303.05 and 323.05 K and pressures up to 18 MPa presents only a vapor-liquid equilibrium (VLE) behavior. The ethane (C2H6)-NN-dimethylformamide binary system behaves quite differently. In fact this latter displays not only a vapor-liquid equilibrium (VLE) behavior but also liquid-liquid equilibrium (LLE) and vapor-liquid-liquid equilibrium (VLLE) behaviors. The ethane-NN-dimethylformamide binary system has been studied at 264.45, 278.55, 293.15 and 313.35 K up to 18MPa. Both systems are correlated using the Peng-Robinson equation-of-state with Wong-Sandler mixing rules. A stability test based on the tangent plan criterion, as described by Michelsen, is carried out during the flash calculations made on the ethane-NN-dimethylformamide binary system.