The invention relates to a method for determining the position of a catheter in a blood vessel relative to a change in the vascular cross section, comprising the steps: providing a catheter that includes at least two electrodes which can be brought into electrically conductive contact with the surrounding blood while the catheter is being positioned in the blood vessel, wherein the two electrodes are installed on the catheter along the longitudinal axis at a defined distance from each other advancing the catheter in the vessel to be treated, toward the change in the vascular cross section and measuring the impedance across the two electrodes while the catheter is being advanced and to a catheter for use in a method of this type.
