The isobaric vapor liquid equilibrium (VLE) data for the systems (thioglycolic acid + water), (thioglycolic acid + butyl acetate), (thioglycolic acid + butyl formate), and (thioglycolic acid + isobutyl acetate) were measured at P = 101.3 kPa by using a vapor recirculating type (modified Rose) equilibrium still. The thermodynamic consistency test of the experimental data for the four binary systems were confirmed by the method of Van Ness. The experimental VLE data were correlated by the three activity coefficient models of Wilson, nonrandom two liquid (NRTL), and universal quasi-chemical (UNIQUAC). The results show that all the calculated data by the Wilson,. NRTL,, and UNIQUAC models are in good agreement with the measured VLE data:.,Meanwhile, the binary interaction parameters of the three models for the binary systems were regressed.