1. The development of sclerosis of the femoral head after fracture of the femoral neck has been investigated by a combined microradiographic and histological examination of twenty femoral heads removed during arthroplasty of the hip done at varying intervals after fracture.

2. Mineralisation of the bone did not differ from the normal.

3. There was a direct correlation between the density of the femoral head as judged radiologically and the width of the trabeculae. In cases of sclerosis of the femoral head the trabeculae were broader than normal and histological examination showed that this was caused by apposition of new bone upon the necrotic trabeculae.

4. Although sclerosis is a result of necrosis, it is at the same time a definite sign that revascularisation and restitution are going on.