Careful measurements of the surface tension of solid polymers, gamma(S), based on the data on contact angles far wetting liquids with various surface tension, gamma(L), allows one to establish the functional dependence of gamma(S) = f(gamma(L)). This dependence is divided into three zones: one zone, where there is no dependence of gamma(S) on gamma(L) and two zones where gamma(S) changes linearly with gamma(L).