Densities and viscosities for binary mixtures of N-methyl-2-pyrrolidinone with cyclohexane, benzene, and toluene were determined at different temperatures and atmospheric pressure. The measurements were carried out over the whole range of composition, using a vibrating-tube density meter and Ubbelohde viscometer. Density, viscosity were used to compute the excess mole volumes, V-E, viscosity deviations, Delta(eta) and the excess energies of activation, Delta G(*E). Results have been fitted to Redlich-Kister equation to derive the coefficients and estimate the standard error values. A discussion on these quantities in terms of molecular interactions is reported. The experimental data of molar volumes are regressed by the Peng-Robinson equation with different alpha function. The mean root mean square deviations between experimental and calculated values for different binary mixtures are no more than 3.5%. (c) 2006 Elsevier Ltd. All rights reserved.