The authors undertook a study of the present indications for lumbar sympathectomy in cases of obliterating arteriopathy of the lower limbs. The principal physiological effects are described in addition to its action on the circulation. Apart from the opening of arteriovenous shunts, the lifting of the precapillary block should be emphasized since this increases the flow and consequently leads to the development of the collateral circulation. A recent experiment over a period of three years involving 457 hospitalized patients is then analysed: out of 371 conservative operations performed, 169 involved restorative arterial surgery and 202 involved only lumbar sympathectomy. Lumbar sympathectomy was combined with the arterial surgery in 150 of the 169 cases quoted above. Lumbar sympathectomy alone is required in stages III and IV when arterial is not possible. At stage II, there is a choice, sympathectomy being preferred to direct surgery. The results are analysed and the best were obtained with patients at stage II.