Morphologically, cortical bone resembles a fiber-matrix composite material such that an osteon is analogous to the fiber while the interstitial bone to the matrix. For example, there have been several studies addressing the mechanical properties of cortical bone based on this point of view (Hogan 1992, Aoubiza et al. 1996). Our interest in cortical bone mechanics stems from the characterization and mechanisms of microdamage such as microcracks in cortical bone. The exponential increase of microdamage in cortical bone tissue has been implicated in increased bone fragility with aging (Schaffler et al. 1995). None of these above mentioned techniques can be conveniently used for our long term study on cortical bone damage mechanics. Recently, significant advances have been made in the mechanics of composite materials. For example, a generalized self-consistent formulation for effective mechanical properties of composites have been developed such that it can apply to the case where the volume fraction of fibers is as high as 80–90% (Huang et al. 1994). In addition, microcracks can be easily included for damage mechanics or fracture mechanics analysis. The objective of this paper is to develop a general scheme for a cortical bone composite model based on the generalized self-consistent method for calculation of effective elastic properties.