The indications for closed intramedullary fixation shaft fractures have been expanded with the advent of interlocked intramedullary nailing. For closed femoral fractures, the indications include most closed Winquist types III and IV fractures, acute fractures, long oblique fractures, and closed reconstructive defects or malrotations. Nail design is important in determining the proximal and distal extent of the fixation, and static or dynamic locking is dictated by the type of fracture. Locked intramedullary nailing of tibial fractures should be approached cautiously. Most reamed intramedullary fixation should be performed on a delayed elective basis.