Controllable stiffness guidewires and methods of using such guidewires are disclosed. According to aspects illustrated herein, there is provided a controllable stiffness guidewire that includes a substantially flexible core wire having a distal section and a proximal section. A plurality of beads may be slidably disposed between the distal section and the proximal section of the core wire. In an embodiment, the beads may be contiguous with one another. The guidewire may further include an actuator designed to compress the beads against one another along the core wire. By compressing the beads against one another, the stiffness of the core wire, and thus the guidewire, can be variably increased between substantially flexible and substantially rigid.