The authors elaborated and tested in 100 patients the described method and were successful in 97%. After local anaesthesia they incise the skin in the inner portion of the skinfold in the cubital fossa and, if necessary, extend it to the bicipital ridge. The best vein as regards access is the v. basilica or the strongest branch of the brachial vein, on both sides. They isolate the vein and insert a thread underneath it. The ends of the thread are grasped by a forceps and thus the vein is fixed. After compressing the arm with a rubber band with subsequent venostasis they puncture the vein on the index finger with sharp scissors. A polyvinyl catheter cut obliquely at the end with an external diameter of 1.5 mm, containing a drip infusion of saline, is inserted slowly into the vein of the sitting patient without positioning of the head, 40-60 cm centrally, with the free hand. The position of the tip of the catheter is checked by X-ray. If there is a venous spasm (the catheter cannot be inserted, its tip is beyond the thoracic cavity or it forms a loop or is bent) the arm is compressed as high as possible. At a short distance the authors insert a catheter into the vein and administer in a drop infusion 40-60 ml 0.3% Xanidil (xanthinolium nicotinicum) solution. After relaxation of the spasm they connect the infusion with the saline, release the rubber band and complete the cannulation. In case of an unintentional injury of the vein they suture it but never use ligatures.(ABSTRACT TRUNCATED AT 250 WORDS)