Relocation and further study of the local endemic Asclepias zacatecana McVaugh showed that it is conspecific with A. schaffneri A. Gray, a distinct species that previously had been synonymized with A. quinquedentata A. Gray. However, we consider a recently described species, A. rzedowskii W.D. Stevens, to be conspecific with A. quinquedentata. Asclepias schaffneri is lectotypified.