The surface tension is an essential property in mass-transfer calculations, since it determines for example the wetting area of a packing in column simulations. Especially for aqueous systems, the use of a simple mixing rule based on mole fractions in general fails. In this work a new simple empirical model is proposed. This model and an, in the literature, often used chemical model have been tested for the description of binary mixtures water + amine. The chemical model has been extended to multicomponent mixtures. The predictions of the empirical and especially the chemical model show good agreement with the surface tensions of aqueous amine blends.