We give a precise counting result on the symmetric space of a noncompact real algebraic semisimple group G, for a class of discrete subgroups of G that contains, for example, representations of a surface group on PSL(2, R)×PSL(2, R), induced by choosing two points on the Teichmüller space of the surface; and representations on the Hitchin component of PSL (d, R). We also prove a mixing property for the Weyl chamber flow in this setting.Theorem A (See Section 5). Let ρ : Γ → G be a Zariski-dense hyperconvex representation. Then there exist h, c > 0, and a probability measure µ on X F , such thatConsidering the constant function equal to 1, one obtains the following corollary.Corollary. Let ρ : Γ → G be a Zariski-dense hyperconvex representation. Then there exist h, c > 0, such thatThe exponential growth rate h in Theorem A is explicit: it is the topological entropy of a natural flow we construct, associated to the representation ρ. On the contrary, not much information is known about the constant c.As first shown by Margulis [18] in negative curvature, in order to obtain a counting theorem one usually proves a mixing property of a well chosen dynamical system. In compact manifolds with negative curvature, the geodesic flow plays this role. In infinite covolume, for example for convex cocompact groups, one should restrict the geodesic flow to its nonwandering set. When ∆ is a lattice in higher rank, use the mixing property of the Weyl chamber flow, to prove the counting result previously mentioned.Let τ be the Cartan involution on g = Lie(G), whose fixed point set is the Lie algebra of K. Consider p = {v ∈ g : τ v = −v} and a, a maximal abelian subspace contained in p. Denote by a + a closed Weyl chamber, and M the centralizer of exp(a) on K. The Weyl chamber flow is the right action by translations of exp(a) in ∆\G/M.