In the present work, thermophysical properties such as density (�), dynamic viscosity (η), refractive index (nD), and surface tension (�) of aqueous piperazine (PZ) solutions with mass fractions (100w = 1.74, 5.16, 10.35) have been measured from temperatures (298.15 to 338.15) K. All of these properties have also been measured for the aqueous blends of N-methyldiethanolamine (MDEA) and piperazine (PZ) with mass fractions 100(w1/w2)= 32.28/1.74, 32.28/5.16, 32.28/10.35, 48.80/1.74, 48.80/5.16, 48.80/10.35) for the entire temperature range. The limit of PZ solubility in water was measured by the addition of a known quantity of anhydrous PZ (solid crystals) in 20 mL of distilled water at temperatures (278 to 343) K with a regular interval of 5 K. The experimental values of the studied physical properties have been compared with the literature and also correlated as a function of temperature. The coefficients of thermal expansion (αp) values have been calculated from their experimental density data using an empirical correlation. A thermogravimetric analyzer (TGA) has been used to explore the thermal stability of the studied solvent systems at a heating rate of 10 °C� min-1. © 2009 American Chemical Society.