DNA/DNA hybridisation analysis was undertaken to resolve the phylogenetic relationships within the chromosomally diverse genus Petrogale. Excepting P. concinna, all full species and three subspecies of P. lateralis were examined; all but four of these 16 taxa were labeled, as were four outgroup species. While demonstrating the ability of the technique to resolve relationships at the species level, our study confirmed that divergence of Petrogale species is recent and occurred during the late Pliocene to mid-Pleistocene. Our data placed the first division within Petrogale species between the monophyletic brachyotis group and the paraphyletic xanthopus plus lateralis/penicillata groups, the latter including P. rothschildi; the subspecies P. l. purpureicollis appears to be intermediate between the lateralis and the penicillata complexes. However, our data could not resolve most relationships amongst the eastern Petrogale radiation, except for a probable grouping of the species P. herberti, P. inornata, P. penicillata, and P sharmani. Finally, our results support recent suggestions that Dendrolagus rather than Thylogale is the sister taxon to Petrogale.