It was made a study to precalculate surface tensions of ternary systems. In the literature, there are given a number of relations for calculating surface tensions of binary systems. However, only a few of them are suitable to predict surface tensions of ternary or multicomponent mixtures. In this paper it was proved the best method for the precalculation of surface tensions using available data from literature and own measurements. Such, the surface tensions of the ternary system n-propanol(1)/ethylene glycol(2)/water(3) were measured over a wide concentration range at 25 degrees C by means of the K12 processor tensiometer developed by Kruss GmbH Hamburg/Germany. Using the recently published equation given by Zhaolin and Zhongxiu in 1995 the best agreement between measured and calculated surface tension of a ternary mixture was obtained.