Bone defects may occur after trauma, infection, or oncologic resection. A critical sized defect is any defect that is unable to spontaneously heal and will require secondary procedure(s) to obtain union. Autologous grafting is widely used, but may be insufficient to obtain union in these situations. Other options include the induced membrane technique, bone transport through distraction osteogenesis, or free vascularized bone transfer. This chapter will review options for obtaining graft, and the aforementioned special techniques for managing these challenging problems.