Densities (&rho) of pure and aqueous N-methyldiethanolamine (MDEA) solutions (wMDEA = 0.3228 or 4 mol·kg-1 and w MDEA = 0.4880 or 8 mol·kg-1) at (298.15 to 338.15) K were measured at atmospheric pressure and also correlated. The coefficients of thermal expansion (α&rho) values were calculated from the experimental density data for the investigated compositions, using an empirical correlation. The excess molar volumes of aqueous MDEA solutions for mole fractions (0.0128 to 0.7531) were calculated from experimental densities at temperatures (298.15 to 338.15) K and correlated with the Redlich-Kister equation. The partial molar volumes of MDEA in water at infinite dilution and the change in volume were also determined using Redlich-Kister coefficients. © 2008 American Chemical Society.