The invention relates to a guide wire for a medical instrument, which has a guide wire core (2) and a sheathing (3) that surrounds the guide wire core at least in sections. According to the invention, the sheathing (3), at least in a shaft section (5) joined to an end section (4), is provided with a rigidity greater than that of the guide wire core. The invention is for use, e.g. in medical instruments for magnetic resonance tomography (MRT) suitable applications.
