Two rock-wallabies were captured in the Victoria Range of the Grampians, the first specimens obtained from Victoria for scientific study. Their chromosomes identified them as Petrogale penicillata and, although the animals appeared to be smaller than their nearest studied conspecifics from Jenolan Caves, N.S.W., 800 km to the north-east, analysis of blood proteins, red blood cell epitopes and parasites indicated little genetic divergence. This lack of differentiation is unusual in a genus in which, further north along the Great Dividing Range, nine chromosomally distinct forms occur within 1500 km. One animal was heterozygous for presence and absence of a major C-band on the second largest chromosome; chromosomes without this band have not been found in other mainland P. penicillata. No electrophoretic variation was detected at 23 genetic loci, even though one allele was unique among P. penicillata so far studied. Although only one extant colony was found, other disused sites were located 30 km further north. Despite the apparent low numbers of animals, there is some evidence that additional colonies may be found.