Abstract: A catheter formed and sized to be traversed through a complex path into a desired location in the body of a human medical patient is disclosed herein. The disclosed device includes a unique means for the deflection of the distal end of the catheter such that it may be easily directed within the patient's venal system. This deflection system exploits hydrodynamic forces produced by bloodflow over distal-end surfaces which are asymmetrically distended in a controlled manner.