Isobaric vapor-liquid equilibrium (VLE) data for the binary mixtures of hexane or octane with 1,2-dimethylbenzene or 1,3-dimethylbenzene were obtained at 101.3 kPa by using a recirculation type of apparatus. All of the experimental VLE data passed the thermodynamic consistency tests of the Herington and the van Ness methods. No azeotrope was found in these binary systems, and each system exhibited large deviations from ideal behavior. The experimental VLE data were correlated well with the Wilson, the nonrandom two-liquid (NRTL), and the universal quasichemical (UNIQUAC) activity coefficient models, respectively. The predictive capability of the universal functional (UNIFAC) and the conductor-like screening model for realistic solvents (COSMO-RS) was also evaluated with the experimental values. These two models fail to quantitatively predict the VLE properties for the octane-containing systems.