The incidence of migration of nails has been shown to be far higher than previously suspected. Its development is influenced by a combination of the characteristics of the fracture, the extent of nail-cortex fixation and when the patient walks. Attempts to protect the fracture site by mobilization in a weight-relieving caliper do not reduce the incidence or extent of migration. The cause of its development appears to be mechanical, resulting from stresses applied to the nail on moving the limb, particularly if weight is being borne. To reduce migration, fixation should be obtained with as large a nail as possible inserted with elastic deformation.