Bone strength and stiffness depend strongly on bone mass, but they also depend on the microarchitecture and tissue quality of both cancellous and cortical bone. All these aspects differ between individuals and between anatomic sites. This review discusses ways to characterize the three-dimensional cancellous architecture as well as changes in architecture and bone composition caused by bone remodeling. The methods used range from detailed descriptions of sizes and distances in cancellous bone to coarser texture analysis methods using clinical data. As the resolution of clinical images increases, it may become possible to use knowledge of the relationship between bone microarchitecture and strength to predict fracture risk clinically.