The study of biomechanical properties of cancellous bone is of growing interest in many fields of medicine especially in the aspect of osteoporosis. Biomechanical properties of bone have been investigated for over 100 years. It was and still it is caused by the necessity of an evaluation of fracture risk. Nowadays, the prediction of osteoporotic fracture is based on bone mineral density measurement which is the most important, but not the only, factor of bone strength. Based on fundamental rules of biomechanics, it is obvious that the strength of each material (cancellous bone too) depends not only on the amount of this material but also on internal structure, shape and biomechanical properties. Ideal method should assess all these properties in vivo and it is looked for. In vitro studies are the base of experimental studies of cancellous bone. The strength tests should be treated as a "gold standard" of them. They allow to improve a knowledge of cancellous bone and to explain the relationships existed between biomechanical properties and bone mineral density, ultrasound parameters and chemical composition. A good knowledge of these relations should help in the diagnostics and monitoring of metabolic bone diseases.