An apparatus and a method for determining the position of a medical instrument, particularly for the purpose of medical navigation. In order to use a simple system to provide a relatively inexpensive technique for determining positional information, the position and/or orientation of the medical instrument is determined by ascertaining the same on the basis of position finding operations. Electromagnetic fields are first measured and the results of relative field strength measurements are taken as a basis for ascertaining the direction of a line from a transmitter to a receiver. After this direction information is known, it is used to determine the positional information of the medical instrument.