Based on fundamental anatomical considerations which are explained in detail we developed a safe technique for the catheterization of the subclavian v.: the point of puncture, which is situated about 25 mm below the junction between the medial and the middle thirds of the clavicle, is accurately determined with the help of a pattern described in the paper. The needle is directed towards the palpable dimple between the spinous processes of the 6th and the 7th cervical vertebrae. The only structure the cannula can reach is the medial portion of the subclavian v. into which the catheter is inserted. Therefore pneumothorax, haemothorax or other incidents do not occur. The method was tested in 350 cases and proved to be absolutely free of complications.