An extruder screw, consisting of a screw shaft with several screw elements, which can be or have been detachably slipped onto this shaft, the screw shaft having an external gearing and the screw elements having an internal gearing, which engages the external gearing, the profile of the teeth of the external and the internal gearing being asymmetric, whereby in relation to a preferred direction of rotation of the extruder screw, the torque-transferring flanks of the teeth of the external and the internal gearing make a smaller angle with the perpendicular to the axis of rotation than do respective opposing flanks, at the tooth, of the external and internal gearing.