Inspired by a fundamental theorem of Bernstein, Kushnirenko, and Khovanskii we study the following Bezout type inequality for mixed volumesWe show that the above inequality characterizes simplices, i.e. if K is a convex body satisfying the inequality for all convex bodies L1, . . . , Ln ⊂ R n , then K must be an n -dimensional simplex. The main idea of the proof is to study perturbations given by Wulff shapes. In particular, we prove a new theorem on differentiability of the support function of the Wulff shape, which is of independent interest.In addition, we study the Bezout inequality for mixed volumes introduced in [SZ]. We introduce the class of weakly decomposable convex bodies which is strictly larger than the set of all polytopes that are non-simplices. We show that the Bezout inequality in [SZ] characterizes weakly indecomposable convex bodies.2010 Mathematics Subject Classification. Primary 52A20, 52A39, 52A40, 52B11.