The mechanical properties of untreated, fully demineralized, and fully deproteinized cortical bovine femur bone were investigated by compression testing in three anatomical directions (longitudinal, radial, transverse). The weighted sum of the stress-strain curves of the treated bones was far lower than that of the untreated bone, indicating a strong molecular and/or mechanical interaction between a collagen matrix and a mineral phase. Demineralization and deproteinization of cortical bone demonstrated that contiguous, stand-alone structures result, shown that bone can be considered as an interpenetrating composite material. Structural features of samples from all groups were studied by optical and scanning electron microscopy. Micro CT-scans were performed on the samples from all three groups for porosity estimation. Anisotropy of mechanical properties of the treated and untreated bone samples were observed: the radial direction was found to be the strongest for untreated bone while the longitudinal one was found to be the strongest for deproteinized and demineralized bones. A possible explanation for this phenomenon is proposed that is attributed to the difference in bone microstructure in radial and longitudinal directions. This research is funded by the National Science Foundation, Division of Materials Research, Ceramics Program (Grant 1006931).