This study deals with the identification of constitutive parameters for hyperelastic materials. Classically, these parameters are deduced from several homogeneous tests. Here, these parameters are obtained from only one multiaxial mechanical test that gives rise to heterogeneous stress / strain fields. Since no analytical relationship is available between measurements and unknown parameters, a suitable tool, namely the virtual fields method, is developed in case of large deformations and used to identify these unknowns. Several results obtained with numerical simulations and experiments performed on rubber specimens illustrate the approach.