Abstract: A ball chain positive drive stepless transmission comprising two V sheaves deployed on a pair of parallel shafts and an endless ball chain serving as transmission medium therebetween and characterized in, each sheave having a V shaped groove formed by two opposite bevel members with an undulating surface readily disposed thereon. Each link of the chain has a ball set adapted to be positively engaged with the undulating surface and also to enable the stepless change of speed while the unit is at rest.