Viscosity (77) and density (p) values are reported for binary mixtures of N-methylpiperazine (NMP) with methanol, ethanol, n-propanol, iso-propanol, n-butanol and iso-butanol over the entire range of mole fraction at 293.15, 298.15, and 303.15 K and atmospheric pressure. The viscosity deviation (Delta eta), excess molar volume (V-E), and excess Gibbs energy of activation (G(*E)) have been calculated. These results were fitted with Redlich-Kister type polynomial equation. All the investigated systems exhibit very large-positive values of Delta eta and G(*E), and negative values of V over the whole composition range. The obvious deviations attribute to the strong cross association between the alkanol and NMP molecules through the hydrogen bond of O-H... N. The temperature has significant effect on Delta eta and relatively slight effect on V-E and G(*E). From the experimental data, the thermodynamic functions of activation have been estimated for each binary mixture. The viscosity data have been correlated with several semi-empirical equations. Two-parameter equation of McAllister can give satisfactory results. (c) 2005 Elsevier B.V. All rights reserved.