The ability of the skeleton to withstand trauma without sustaining a fracture is a function of its inherent strength. Like any other load-bearing structure, this depends on the amount, distribution and quality of the structural elements. Several disease processes can weaken the skeleton but few diseases affect it to the same extent as the normal aging process, which remains the most common cause of diminished skeletal strength, often to the point where spontaneous fractures occur. In this article we will discuss the effects of aging on the amount, distribution and quality of the skeleton in order to examine why trauma is more likely to result in fracture in the elderly.