Benois O., Bodineau T., Butta' P., Presutti E. On the validity of van der Waals theory of surface tension (88K, plain TeX) ABSTRACT. In this paper we prove a weak large deviation principle for the empirical distribution of Ising spins in $d\ge 2$ dimensions when the interaction is determined by a Kac potential and the temperature is below the critical value. We prove that the rate function is proportional to the area of the interface by a factor which identifies the surface tension. Its value is the same as that predicted by the van der Waals theory.