The mountain pygmy-possum, Burramys parvus, exists in isolated and fragmented populations in the Australian alps. To examine the degree of interpopulation divergence, mitochondrial cytochrome b and NADH dehydrogenase subunit 2 (NADH2) sequences were obtained from samples representing all populations of B. parvus. Three divergent mitochondrial DNA (mtDNA) lineages were identified which exhibited strong phylogeographical structure. This indicates the presence of three maternal clades corresponding to populations in the northern, central and southern Australian alps. Molecular clock estimates suggest that the mtDNA lineages diverged from one another 420-680 thousand years ago. On this basis it is argued that B. parvus populations have probably been isolated since the mid-Pleistocene, and that management should focus on maintaining viable B. parvus populations in each of the three regional localities.