Isobaric vapor-liquid equilibrium (VLE) data for two binary systems, tetrahydrofuran (THF) + 1,4-butanediol (BDO) and THF + gamma-butyrolactone (GBL), were measured at pressures of 50.0 and 70.0 kPa. The experiment data were regressed using maximum likelihood method, and binary interaction parameters were estimated for Wilson, NRTL, and UNIQUAC activity coefficient models by Aspen Plus V9.0. All of the models match well with the experimental data. All the experimental data passed the thermodynamic consistency test by Redlich-Kister area test and Van Ness test. The two binary systems both exhibit positive deviations from ideality.