In a previous work, the writers have described the influence of vasomotoricity on the shape of the ultrasonic velocimetric curves (Doppler). A vasodilatation induced by an anaesthesia of the sympathetic chain or by a general anaesthesia by penthotal produces a raising of the whole curve above the basic line. The writers have studied in the present work the shape of the velocimetric curves after a lumbar sympathectomy and have compared them with the variations of the cutaneous thermometry and with the clinical results. A correlation has been found in 86.3% of the 124 studied limbs. The study shows that the raising of the curve due to the phenomenon of vasodilatation appears only at the extremity of the limb. The profile of the curve remains unchanged at the root. A velocimetric curve above the basic line may occur apart from any vasomotoric modification. In this case it is the sign of an up-stream obliteration combined with a drop of the index of perfusion (less than the unit).