Based on the modified Othmer still, an instrument is developed for vapor-liquid equilibrium (VLE) measurements in a microwave field. The isobaric conventional binary VLE experimental data compare favorably with the literature data and the results predicted from the universal quasi-chemical (UNIQUAC) model, which also verifies the reliability of the new instrument. A systematic experimental study of the effects of a microwave field on the VLE for the binary mixtures is reported herein for the first time to the best of the author's knowledge. Isobaric VLE data for two binary systems, benzene/ethanol and DOP/iso-octanol, at 101.33 kPa are determined under conventional conditions and various microwave fields. The results clearly demonstrate that the VLE of benzene/ethanol in a microwave field is shifted compared to the conventional condition; no change is observed in the DOP/iso-octanol binary system. It is concluded that the ethanol can be vaporized selectively because the rate of microwave energy absorption of ethanol is higher than the rate of heat transfer from ethanol to benzene. Furthermore, various microwave irradiation powers and the dielectric constants of the binary mixture are chosen to investigate the influence of the microwave irradiation on the VLE. The results indicate that microwave field strengths from 25 W to 200W have varying effects on the VLE. The results also show that the effect of the microwave field on VLE is more prominent in the binary system with a larger dielectric constant difference between the two substances. (C) 2013 Elsevier Ltd. All rights reserved.