The disclosure of this application relates generally to medical devices and in particular to a steerable medical instrument applicable to guide interventional tools and instruments, such as percutaneous biopsy and ablations tools and endoscopes. The steerable medical instrument has an outer and an inner tube where the inner tube is movable at the proximal end and fixed at the distal end. At least one of the outer tube and inner tube has a plurality of openings, which creates deformable portions so that the outer and the inner tubes can bend by moving the inner tube at the proximal end.