Australian brush-tailed rock-wallabies (Petrogale penicillata) became naturalized on Oahu, Hawaii, after the accidental liberation of 2 animals (of unknown wild provenance) in 1916. Subsequently, Australian P. penicillata has experienced widespread local population extinctions as part of an ongoing decline. Thus, the P. penicillata population in Hawaii could represent an important conservation resource. In addition, there have been suggestions that the rock-wallaby population in Hawaii is distinct from Australian P. penicillata. In this study a multifaceted molecular genetic analysis (chromosomes, allozymes, mitochondrial DNA [mtDNA] control region) was undertaken to compare Hawaiian Petrogale with P. pencillata from throughout the species' natural range in southeastern Australia. Hawaiian Petrogale were found to possess a 2n = 22, all acrocentric, karyotype characteristic of P. penicillata. The allozyme (41 loci) and mtDNA profiles of the Hawaiian animals indicate that they were originally derived from northern P. penicillata populations, most likely in southeast Queensland. These results confirm that the Petrogale in Hawaii represent typical P. pencillata and are not consistent with suggestions that the Hawaiian population represents a novel taxon.