Abstract : This study addresses the stochastic modeling of media whose elasticity tensor exhibits uncertainties on the material symmetry class to which it belongs. More specifically, we focus on the construction of a nonparametric probabilistic model which allows realizations of random elasticity tensors to be simulated, under the constraint that the mean distance (in a sense to be defined) to a given class of material symmetry is specified. Following the eigensystem characterization of the material symmetries, the proposed approach relies on the nonparametric probabilistic model in which a new ensemble SE++ of symmetric positivedefinite random matrices, allowing the variance of selected stochastic eigenvalues to be partially prescribed, is introduced and defined having recourse to the MaxEnt principle. A new methodology and parameterization of the model are then defined.