A guidewire torque device formed from a single piece that may be either molded or machined. The device includes an insertion slot for receiving a guidewire, such that the device does not have to be backloaded over the end of the guidewire. Two rotation slots, provided in opposite sides of the device, allow the device to be rotated so as to secure the guidewire within the device. The rotation slots terminate at a hole in the center of the device that is sized to secure a guidewire of a selected diameter. The device can be operated by a physician with a single hand, and is particularly useful during rapid exchange procedures.