A medical bone screw in particular in pedicle screw design includes a screw-and-thread shaft which has a distal shaft portion of a preferably smaller core diameter that transitions into a proximal shaft portion of a preferably larger core diameter, whose proximal end is provided with a screw head. The core cross-sectional shape along the distal shaft portion is formed to be out-of-round, preferably polygonal, and the core cross-sectional shape along the proximal shaft portion is formed to be circular.
