Intra-medullary pressure and intra-osseous phlebography have been studied in the femurs of ten paraplegics. These methods are reliable for studying bone circulation. Results show that there exists an increase of intra-medullary pressure of more than twice the normal value and signs of delayed blood flow as well as a diaphyseal reflux in the bone. The blood gases are also modified (O2 saturation; pO2 and pCO2). These signs indicate that there is a venous stasis. These circulatory disturbances are due to an autonomic nervous system lesion. Furthermore it seems that these vascular modifications below the neurological lesion have an influence on the osteoporosis in paraplegia.