Animal models with well defined bone status of osteoporosis are helpful for testing of bone substitutes for human osteoporotic bone. In the present poster, the mechanical properties of vertebrae of osteoporotic rats are investigated. Mature Sprague Dawley rats were divided into two groups before Sham surgery or ovariectomy (OVX). The Sham group had free access to food and water, whereas the OVX rats were fed a compromised diet. Computer tomograms of rat vertebrae were transformed into a voxel-based finite element model and uniaxial compression tests of the vertebrae similar to real tests were performed. By comparing the simulation results with real measurements, the change of the microscopic Young's modulus during osteoporotic bone development was determined. Relationships between the morphological and mechanical features of the vertebrae of healthy and osteoporotic rats at different times are discussed. For a deeper insight into the osteoporotic bone development, a voxel-based mathematical model of bone growth was implemented. This model comprises a finite element calculation of the bone deformation under mechanical loading. The present computer experiments could help in the adaption of implants to the special characteristics of osteoporotic bone. The change of the elastic bone properties during osteoporotic bone development, as found by our investigations, should be included in further modeling of osteoporotic bone.