1. The surgical treatment of idiopathic aseptic necrosis of the femoral head has been reviewed in the light of experience gained from 240 hips operated upon.

2. When pain is not severe and the necrosis of bone as seen in serial radiographs is not rapidly progressive, simple observation and palliative medical treatment are indicated.

3. When pain disables the patient and collapse of the head is progressive, operation is indicated. If radiographs show necrosis limited to the anterior part of the head and sparing an arc of at least 20 degrees of the lateral part, either an osteotomy bringing the shaft into adduction and flexion or an "adjusted cup" arthroplasty is indicated, with a preference for the latter because it gives better results in a shorter time.

4. If at arthrotomy the necrosis appears to involve the posterior slope of the head, prosthetic replacement, preferably total, should be undertaken.