The ball-worm (BW) is a new type of mechanism created by adding a sequence of rolling balls between the worm and gear components of a worm mechanism. This eliminates the sliding friction between the components, which improves the performance of the mechanism. The advantages of the BW are similar to those of the well known ball-screw mechanism: low backlash, high precision, low friction, high efficiency, higher power transmission in a lower size, etc.