Guidewire for a catheter, which is designed for introducing and/or removing fluids into/from human and/or animal hollow organs, in particular blood vessels, comprising a) an elongate hollow shaft with a lumen for the delivery and/or withdrawal of the fluid, and b) an insertion aid in the form of a flexible wire coil attached coaxially to a distal end of the hollow shaft, with a guidewire tip arranged at a distal end of the wire coil, c) wherein a core wire is arranged in the lumen of the hollow shaft in order to control a flexibility of the guidewire, which core wire extends out of the lumen in a longitudinal direction through the wire coil as far as the guidewire tip; d) a distal inner region of the wire coil, adjacent to the guidewire tip in a proximal direction, communicates with the lumen of the hollow shaft via a fluid channel (151, 161, 155) formed alongside the core wire and has at least one outwardly open through-opening for the fluid that is to be introduced and/or removed, and e) a fluid-permeable connection between wire coil and core wire is present in a region of a proximal end of the wire coil, such that the wire coil is mechanically fixed relative to the core wire, and the distal inner region of the wire coil communicates with a proximal inner region of the wire coil lying proximally from the fluid-permeable connection, characterized in that f) the fluid-permeable connection is present as a cohesively bonded connection, wherein a tube extending parallel to the core wire and embedded in the fluid-permeable connection is present as a channel-like passage for the fluid that is to be delivered and/or withdrawn, wherein the tube is cohesively embedded all the way round in a soldering compound and connected to the wire coil. a) an elongate hollow shaft with a lumen for the delivery and/or withdrawal of the fluid, and b) an insertion aid in the form of a flexible wire coil attached coaxially to a distal end of the hollow shaft, with a guidewire tip arranged at a distal end of the wire coil, c) wherein a core wire is arranged in the lumen of the hollow shaft in order to control a flexibility of the guidewire, which core wire extends out of the lumen in a longitudinal direction through the wire coil as far as the guidewire tip; d) a distal inner region of the wire coil, adjacent to the guidewire tip in a proximal direction, communicates with the lumen of the hollow shaft via a fluid channel (151, 161, 155) formed alongside the core wire and has at least one outwardly open through-opening for the fluid that is to be introduced and/or removed, and e) a fluid-permeable connection between wire coil and core wire is present in a region of a proximal end of the wire coil, such that the wire coil is mechanically fixed relative to the core wire, and the distal inner region of the wire coil communicates with a proximal inner region of the wire coil lying proximally from the fluid-permeable connection, characterized in that f) the fluid-permeable connection is present as a cohesively bonded connection, wherein a tube extending parallel to the core wire and embedded in the fluid-permeable connection is present as a channel-like passage for the fluid that is to be delivered and/or withdrawn, wherein the tube is cohesively embedded all the way round in a soldering compound and connected to the wire coil.