Mitochondrial DNA (mtDNA) analysis was undertaken to resolve the systematic uncertainties surrounding the morphologically distinct purple-necked rock-wallaby (P. lateralis purpureicollis) of north-west Queensland, Australia. A comparison of mtDNA sequence divergence using both whole mtDNA restriction site and control-region sequence analyses revealed that P. l. purpureicollis was as well differentiated from other P. lateralis (black-footed rock-wallaby) taxa as P. lateralis was from P. penicillata (brush-tailed rock-wallaby) or P. assimilis (allied rock-wallaby). Phylogenetic analysis of the sequence data suggests that P. lateralis (sensu lato) is paraphyletic, with P. l. purpureicollis being more closely aligned to P. penicillata and P. assimilis than to P. lateralis (sensu stricto). Data are also presented that demonstrate significant differences in the distribution of the telomeric repeat sequence (TTAGGG)n between the chromosomes of P. l. purpureicollis and the karyotypically similar MacDonnell Ranges race of P. lateralis. In addition, meiosis appears to be severely disrupted in the majority (73%) of oocytes examined from two P. l. purpureicollis x MacDonnell Ranges race hybrids. In light of these findings we recommend that the purple-necked rock-wallaby be reinstated as a full species, P. purpureicollis Le Souef 1924.