Isobaric vapor-liquid equilibrium (VLE) measurements at 40.0,53.3 and 66.7 kPa (300,400 and 500 mmHg) of aqueous N-methyldiethanolamine (MDEA) solutions were performed using a modified ebulliometer. The concentration of MDEA in the liquid phase ranged from about 0.06 to 0.93 in mole fraction and the temperatures from about 76 to 186degreesC. The data measured in this work, along with other experimental data taken from the literature, are used for the improvement of the thermodynamic modeling of the water/MDEA binary system. (C) 2004 Elsevier B.V. All fights reserved.