Abstract: A guidewire includes a core and a coil in composite cooperation to enable the guidewire to be used within tortuous regions of the vasculature. The core has a proximal region and a distal region. The distal region includes a flattened end and a tang for connecting the core to the coil. The coil has a proximal end, a distal end and a length extending between the proximal end and the distal end. The ratio between the proximal region and the coil diameter is 1.4:1 or greater. The guidewire includes three joints for attaching the coil to the core. A distal joint attaches the distal end of the coil to the flattened end of the core. A proximal joint attaches proximal end of the coil to the core. A medial joint attaches the length of the coil to the tang. The three joints cooperate with the 1.4:1 ratio to improve torque transmission ability of the guidewire to enable the guidewire to steer through vessels with bends of over 90 degrees and with lumen diameters of less than 3 mm.