The purpose of this paper is the construction of an uncertain probabilistic model for the mechanical properties of the cortical bone. The main objective is firstly to propose a probabilistic simplified model adapted to the ultrasonic axial transmission technique and secondly to present an experimental identification using this technique. The simplified model is constructed as a fluid-solid semi-infinite multilayered system in which the solid layer (the cortical bone) is a homogeneous anisotropic elastic material and the two others semi-infinite layers are fluids. This model is a rough approximation of the real biomechanical model and it can be improved by taking into account the uncertainties related to the elasticity tensor with a probabilistic model. In this paper, the parameters of the probabilistic model are the mean elasticity tensor and a dispersion coefficient. A complete application is presented for the human cortical bone for which an experimental database is available.