The gummy shark (Mustelus antarcticus) is the main target of southern Australian shark fisheries. Its stock structure was investigated through allozymes (up to 28 loci), mitochondrial DNA (up to 10 restriction enzymes) and vertebrae counts. The average heterozygosity per allozyme locus (0.099) and degree of polymorphism (0.255) was high for sharks. Composite mitochondrial DNA haplotype diversity (0.534) and mean nucleotide sequence diversity (0.16%) were also moderately high. Three of the seven polymorphic allozyme loci (CK-A*, LDH-1*, PEP*) and the mtDNA haplotypes showed significant spatial differentiation. Two genetic stocks were identified: one along the southern coast of Australia from Bunbury in Western Australia to Eden in New South Wales and one off northern New South Wales (in the region of Newcastle to Clarence River). There was some evidence for a third stock off Townsville, Queensland. The northern occurrences extend the known geographical range of this species. Vertebrae counts from Eden northwards increased, supporting the conclusion of population heterogeneity off eastern Australia.