Eighty-seven pertrochanteric fractures consecutively treated between the years 1978 and 1981 are reviewed. External and internal rotation types are described relative to their aetiology. The final typing of the fracture can be made only on reduction. What we have called 'internal rotation fractures' show an excellent correlation with the unstable fracture gradings described by Boyd, as well as very osteoporotic Singh gradings (1-3). It is contended that the latter is the main factor in its production as opposed to the more common external rotation variety. An appeal is made for recognition of the fracture, its reduction by means of external rotation and adequate fixation. Early weight bearing is not advised, in order to prevent subsequent varus deformity with extrusion of the implant.