Two bone biopsies are proposed to each patient (just before the renal transplantation procedure, already on general anaesthesia, and circa 12 months after transplantation, with local anaesthesia). Bone biopsies will be made using a 7G trocar (Osteobell T), by manual puncture. After processing the bone fragment (fixation, dehydration and methylmethacrylate impregnation), routine staining will be used: von Kossa, Goldner trichrome, acid phosphatase (selective staining of osteoclasts), and Perls. Cortical bone will be evaluated separately from trabecular bone. Cortical bone volume and cortical thickness will be measured. Bone biopsies will be described for: bone remodelling and degree of cellular activation (specific score); efficacy of mineralization; quantification of possible metal deposits. In order to evaluate the rate of bone formation and rate of mineral deposition, the patient will be prescribed tetracycline hydrochloride, 500mg, 12/12 hours for three days, one month and one week before the 2nd bone biopsy or, in the case of live donor transplantation, before the 1st and 2nd bone biopsy.