Isobaric vapor-liquid equilibrium (VLE) measurements are reported for binary mixtures of tetrahydrofuran and tetrahydropyran with (1-methylethyl)benzene at 97.3 kPa. The data were obtained using a vapor recirculating-type (modified Othmer's) equilibrium still. Both mixtures show negative deviation from ideality. None of the systems form an azeotrope. The experimental data obtained in this study are thermodynamically consistent according to the Herington and Black tests. The activity coefficients have been satisfactorily correlated by means of the Margules and NRTL equations. Excess Gibbs free energy has been calculated from the experimental data. The vapor-liquid equilibrium predictions have been done by the UNIFAC group contribution method too.