Multishafted, continuous mixing and kneading of plastifiable compounds using mutually engaging worm elements which rotate in the same sense, at a constant axial separation. Along the direction of advance, the worm elements have successive zones with different numbers of threads. Each zone with the smaller number of threads follows a zone with a larger number of threads. The worm elements mesh with one another in successive zones so that the worm element of one zone has a self-cleaning action upon one another, and the zone with the smaller number of threads has a housing with a larger interior bore and larger corresponding worms than the zone with the larger number of threads, so that, in the zone with the smaller number of threads, the free cross-section is larger than in the preceding zone. Both zones have fill openings that can be charged independently of one another.