A guide wire (1) for use with a catheter comprises a core wire (3) terminating in a distal portion (18) of flat ribbon-like construction having respective opposite major surfaces (29,30). A spring (24) is brazed to a distal end (27) of the distal portion (18) and to the core wire (3) at a tapering portion (14). A reinforcing member (38) extends axially along the distal portion (18) from a proximal end (26) of the distal portion (18) to a location (40) for reinforcing the distal portion (18) for in turn increasing its torsional rigidity in order to minimise axial twisting of the distal portion (18). A guide portion (42) of the distal portion (18) between the location (40) and the distal end (27) is provided to be bent at a desired set curved configuration for offsetting a distal tip (9) of the guide wire (1) from a central axis (8) thereof, so that by rotating the guide wire (1) at its proximal end (5) the distal portion (18) is also rotated for aligning the distal tip (9) with a branched vessel into which it is desired to direct and urge the guide wire (1).