All intramedullary nailing creates some loss of endosteal blood supply and an increase in intramedullary pressure, resulting in marrow embolization. In laboratory studies, both reamed and nonreamed intramedullary nailing have led to alteration in selected pulmonary variables. This effect, although transient, appeared more pronounced with reamed techniques than with nonreamed techniques. Concern about the systemic pulmonary effects of reamed intramedullary nailing has led to an increase in the use of nonreamed nailing. The authors of most clinical studies have reported that reamed intramedullary nailing has not been associated with a concomitant increase in pulmonary complications in multiply injured patients, although this point is still controversial. Femoral shaft fractures treated with nonreamed nailing have been shown to have slightly higher rates of delayed union and nonunion compared with those treated with reamed nails. Reamed interlocking intramedullary fixation remains the treatment of choice for femoral shaft fractures in adults. Further study is required to determine whether an identifiable subgroup of trauma patients is adversely affected by intramedullary reaming, which would suggest the need for alternative fixation techniques.