1. Recently described histological and radiographic methods of diagnosing osteoporosis have been applied to patients with transcervical and intertrochanteric fractures of the femur.

2. Both methods indicate a higher incidence of osteoporosis in such patients than in a control series, especially in older women with intertrochanteric fractures.

3. A discrepancy between the results of biopsy and radiographic examination was encountered, the explanation of which is not yet clear.

1. Some physical properties of living and dead bone have been studied in rats; most of these are interrelated and ultimately depend upon the composition of the tissue.

2. Dead bone, remaining within the body, does not take up measurable amounts of mineral from the tissue fluid but retains its original physical properties of radiographic density, specific gravity, strength and composition.

3. The altered radiographic density of avascular bone seen in clinical practice is almost certainly relative unless there has been concomitant appositional new bone formation.

4. Some other explanation must be sought for the finding that dead bone takes up significant amounts of bone-seeking isotopes in radioactive tracer studies.

A patient with Paget's sarcoma of the femur, alive and well seven years after amputation, is reported. Long survival in two previously reported cases is also mentioned.