Rebutia formerly included a large number of species. In recent years studies of DNA have shown that the original genus was derived from different evolutionary lines, and the group has now been split into Rebutia and Aylostera. One of the obvious differences between the two is that on the flowers, the stalk is hairless (naked) on Rebutia whereas on Aylostera it has hairs or bristles.
The genus Rebutia currently comprises twelve species according to Mosti et al. (2011):