This study investigated the relationship of bone porosity and bone-cement interface shear strength. One hundred forty-six samples were taken from the distal metaphysis of 20 bovine femora. After cementation, the shear strength of the bone-cement interface was tested. According to the porosity, the samples were divided into four groups. Group I (porosity /=90%) 14.85 MPa. The differences between the four groups were statistically significant. Greater porosity yielded a stronger bone-cement interface shear strength under the identical cementation technique. The optimum porosity of cancellous bone is more than 90% which can be found by reaming or drilling to deeper bone in cemented acetabular fixation.