Abstract: A system for detecting and monitoring the position of a catheter tip during insertion and after placement of the catheter in a body cavity. A coupling means such as an inductor coil is secured adjacent the catheter tip, and leads extend from the coil along the catheter for connection to external indicating equipment. Energy is propagated through the body to the coupling means from an external source such as an oscillator-driven coil or coils, and relative proximity and orientation of the external and catheter coils is determined by monitoring amplitude and phase of the signal induced in the catheter coil.