Department of Chemistry, Agra College, Agra-282 002, Uttar Pradesh, India E-mail : mukhtarsingh2003@rediffmail. com Mnuscript received 29 May 2006, accepted 7 November 2006 Densities and viscosities of binary and ternary mixtures of o-nitrotoluene with methyl alcohol, benzene, toluene, carbon tetrachloride and 1,4-dioxane have been determined at 298.15 K over the whole composition range. From density and viscosity data, viscosity deviations (Δη) and excess thermodynamic functions, viz. the molar ''volume (VE) and the excess Gibbs free energy of activation of viscous flow (ΔG#E) have been calculated in respect of binary and ternary liquid mixtures at 298.15 K and fitted by Redlich-Kister and Cibulka equations respectively. From the small magnitude of the values of standard deviation it is concluded that the experimental values of Δη,VE and ΔG#E compare fairly well with the corresponding theoretical values predicted by Redlich-Kister and Cibulka equations for binary and ternary mixtures respectively.