We analysed the mtDNA control region (HV1) of 93 tissue samples from all five populations of the saiga antelope Saiga tatarica. The results show a slight but clear distinction between S. t. mongolica and S. t. tatarica, supporting the current designation of S. t. mongolica as a subspecies rather than a separate species. Levels of genetic diversity were low in S. t. mongolica, consistent with the small size of its population and long isolation. Although populations of S. t. tatarica have reasonable levels of genetic diversity, their conservation status is perilous. The Kalmykian and Kazakhstan samples each contained unique haplotypes, although the species as a whole appears polyphyletic, consistent with recent fragmentation and rapid population decline. An understanding of the population genetics of this species is an essential prerequisite for conservation action.