The aim of this study is to assess density and elastic properties of Wistar rat cortical bone from growth to senescence and to correlate them with morphological and physico-chemical properties of bone. During growth (from 1 to 9 months), bone density and Young's modulus were found to increase from 1659+/-85 to 2083+/-13 kg m(-3) and from 8+/-0.8 to 19.6+/-0.7 GPa respectively. Bone microporosity was found to decrease from 8.1+/-0.7% to 3.3+/-0.7%. Physico-chemical investigations exhibited a mineralization of bone matrix and a maturation of apatite crystals, as protein content decreased from 21.4+/-0.2% to 17.6+/-0.6% and apatite crystal size and carbonate content increased (c-axis length: from 151 to 173 A and CO(3)W%: from 4.1+/-0.3% to 6.1+/-0.2%). At adult age, all properties stabilized. During senescence, a slow decrease of mechanical properties was first observed (from 12 to 18 months, rho=2089+/-14 to 2042+/-30 kg m(-3) and E(3)=19.8 +/-1.3 to 14.8+/-1.5 GPa), followed by a stabilization. Physico-chemical properties stabilized while microporosity increased slightly (from 3.3% to 4%) but not significantly (p>0.05). A multiple regression analysis showed that morphological and physico-chemical properties had significant effects on density regression model. Microporosity had a greater effect on Young's modulus regression model than physico-chemical properties. This study showed that bone structure, mineralization and apatite maturation should be considered to improve the understanding of bone mechanical behaviour.