An expression based on molecular thermodynamic considerations was developed for representing surface tensions of pure polar liquids and their mixtures. Contributions to surface tension from hard spheres, dispersion, and polar-polar interactions were considered and assumed to be additive in the development. The Davis theory (J. Chem. Phys. 62 (1975) 3412, Adv. Chem. Phys. 49 (1982) 357) and the simplified radial distribution function expression of Xu and Hu (Fluid Phase Equilibria 30 (1986) 221) were adopted in the model development. Two pair-potential parameters, size and energy, were used for each pure fluid. In addition, one adjustable parameter was used for each binary system, but two adjustable parameters were required for binary systems containing water. The average absolute percentage deviations obtained for arbitrarily selected 22 pure polar compounds, 12 non-aqueous binary polar systems and four binary aqueous systems (excluding ethanol + water and 1-propanol + water) are 0.59, 0.58 and 2.40, respectively. In addition, the proposed approach was extended to mixtures containing polar and non-polar compounds with reasonably good results. Feasibility of the proposed model for predicting surface tension for multicomponent (ternary) mixtures was demonstrated.