Bone metabolism has been assessed in 36 hemiplegic patients (18-77 years), 26 with CVA and 10 with head injuries. The results show an increase of serum calcium and phosphorous levels in the first month as well as hydroxyprolinuria. The radiological examination showed signs of demineralisation, as well as single photon absorptiometry of both arms. Bone scan by 99Te demonstrated a hypercaptation in both paralysed limbs. From the 36 patients, 17 had a 47Ca kinetic study which showed an average of normal values as far as bone accretion (Vo+) is concerned. However, the two youngest patients (18 and 32 years) had a high value of this parameter. The urinary calcium excretion (Vu) and the fecal calcium excretion (Vf) was also increased in the 17 patients. The bone resorption measured by Vo- was also high at the beginning of the study and significantly decreased 12 months later. Our observations show that neurologic osteoporosis of the hemiplegic patient is related to an unbalance between the synthesis and the degradation of a bone whose metabolism is active. Related to the determination of the intramedullary pressure and intraosseous phlebography, it seems that this resorption is due to a venous stasis. This circulatory modification regime can influence cell differentiation and probably be responsible in a way for this osteoporosis.