Breast, prostate, lung, and other cancers can metastasize to bone and lead to pathological fracture. To lay the groundwork for new clinical techniques for assessing the risk of pathological fracture, we identified relationships between density measured using quantitative computed tomography (ρ_QCT), longitudinal mechanical properties, and ash density (ρ_Ash) of cortical bone from femoral diaphyses with and without metastatic lesions from breast, prostate, and lung cancer (bone with metastases from six donors;​ bone without metastases from one donor with cancer and two donors without cancer). Moderately strong linear relationships between ρ_QCT and elastic modulus, strength, and ρ_Ash were found for bone with metastases (0.73 < r < 0.93, P < 0.05). After accounting for differences in ρ_QCT, the elastic modulus, compressive strength, tensile yield strain, and ρ_Ash of bone with metastatic lesions differed from those of bone from donors without cancer (P < 0.01). However, differences in tensile strength or compressive yield strain, after controlling for ρ_QCT, were not found. Thus, these cancers degrade the elastic modulus and compressive strength, but not the tensile strength, of cortical bone beyond the amount that would be expected from decreased density alone. The ρ_QCTmechanical property relationships reported may be useful for evaluating bone integrity and assessing the risk of fracture of bone with metastases.