Bone is a composed structure including cortical bone, trabecular bone and bone marrow, but organization of these composites changes during ageing; indeed, differences can be shown from childhood to old age. But these changes in childhood are not clearly shown. For example, certain studies compare bone density (Bone Mineral Density : BMD) of children, like in Chron disease (Edisio et al, 1999), but not the stiffness, strength or elastic modulus. Some have chosen specific bone, close to cancellers cells (Baleani et al., 2008), or cadaver fragments (Currey, 1975). The aim of this study was to determine the elastic properties of the children bone. We have used surgery waste (bone transplantation) from long bone (fibula: essentially composed of cortical bone) of children without metabolic or mineralization disturbances. A specific ultrasound frame able to process very small sample (36 mm high, 11 mm tall, and 0.2 mm thickness) was used to evaluate velocity grading along bone axis. They are moved with 0.1 mm accuracy in x and y axis. For Z axis, azimuth got 0.01° of accuracy (Fig 1). Nominal frequency can increase from 3 to 10 MHz. Our first results (two samples) show longitudinal (vL) and transversal (vT) velocity of propagation (values in m.s-1) We used the same method as used for isotropic transverse bovine bone frame. In the case of orthotropic we can right 12 elements of rigidity matrix. Comparisons were made between juvenile specimens and mature specimens, and the first result is that the wave velocities, and the associated elastic modulus, are then lower in children than adult around 30 percent less for 11 years old child.