A guide wire for a medical instrument, such as an endoscope, has a marking pattern, which extends at least across part of the axial length of the guide wire and includes markings of different marking types that can be sensed. On the guide wire, markings of first and second marking types are formed by marking surfaces, of which the marking surfaces of at least the first marking type each extend across only part of the circumferential surface of the guide wire and across only part of the axial length of the marking pattern, and in the axial direction of the guide wire follow each other at a distance by at least one interposed marking surface of the second marking type. At least one longitudinal marking strip is formed as a marking of a third marking type, which extends continuously across the axial length of the marking pattern.