A case of a lost guide wire extending from the vena cava to the back of the neck after central venous catheterization is presented. A trainee inserted a central venous catheter via the left subclavian vein in a 40-year-old male patient after surgery, but did not notice that a guide wire was completely inserted in the vein. After 6 months, the lost guide wire was seen extending from the saphenous vein through the vena cava, right atrium, right ventricle, pulmonary artery and lung tissue to the back of neck. Although percutaneous catheterization of central veins is a routine technique, it is a procedure requiring advanced surgical skills, expert supervision, and attention to detail in order to prevent adverse effects. The present case is not only a technological problem, but also one of responsibility. The operator must hold onto the guide wire at all times until removal from the vessel, and a supervisor must make sure that trainees are aware of all possible complications.