1. The radiological appearances of the fragments in 100 trochanteric fractures have been analysed. 2. A simple practical classification enables the correct method of reduction to be chosen. 3. In Type I fractures the proximal fragment consists of the head and neck alone. In Type II fractures the head, neck and a major part of the great trochanter constitute the proximal fragment. 4. The key role of the greater trochanter in influencing the displacement of the fragments is discussed. 5. For reduction, Type I fractures require rotation of the distal fragment to a neutral position. Type II fractures reduce in some degree of lateral rotation.