Exchange nailing is most appropriate for a nonunion without substantial bone loss. There is no clear consensus regarding the use of exchange nailing in the presence of active, purulent infection. The exchange nail should be at least 1 mm larger in diameter than the nail being removed, and it has been recommended that it be up to 4 mm larger when the nail being removed was greatly undersized. Canal reaming should progress until osseous tissue is observed in the reaming flutes. Exchange nailing is an excellent choice for aseptic nonunions of noncomminuted diaphyseal femoral fractures, with union rates reported to range from 72% to 100%. On the basis of the available literature, exchange nailing cannot be recommended for distal femoral nonunions at this time. Exchange nailing is an excellent choice for aseptic nonunions of noncomminuted diaphyseal tibial fractures, with union rates reported to range from 76% to 96%. On the basis of the available literature, exchange nailing is generally not indicated for humeral nonunions.