The postablation bone marrow regeneration model is an in vivo paradigm of synchronous bone formation and resorption restricted to a defined reference anatomical location. The blood clot that fills the medullary cavity immediately after marrow removal is organized by replacement with primary cancellous bone. At the peak of the osteogenic phase almost the entire medullary cavity is filled with the trabecular mesh. The primary bone trabeculae are then subjected to osteoclastic resorption and replacement by intact marrow. Since in animals of defined strain, sex and age the timing and extent of formation and resorption are highly reproducible, the postablation model in combination with simple vital methods and/or bone histomorphometry as well as molecular and biochemical approaches applied at specified time periods provides an efficient in vivo tool to assess the efficacy of antiresorptive agents as well as their possible adverse effects on bone formation. When applied to transgenic animals this model may become useful to determine the role of individual genes in matrix formation, mineralization and resorption.