To facilitate an understanding of the dependence of ultrasound velocity and attenuation upon the material and structural properties of cancellous bone, several theoretical concepts for ultrasound propagation have been adapted or developed, including the Biot theory and several scattering theories. Biot theory considers wave propagation through an elastic porous solid interspersed with fluid, considering the separate motion of the trabecular framework and morrow, respectively. The success achieved with the Biot theory has, to date, tended to be greater for the prediction of velocity than for attenuation. This article provides a review of the relevant literature, describing the physical parameters required for the Biot theory and their experimental determination. It is suggested that future developments should consider additional attenuation mechanisms, in particular, those due to scattering, local flow in microcracks, and surface roughness of the trabeculae.