A cladistic analysis of nucleotide substitutions in the 16S ribosomal RNA and cytochrome oxidase subunit I genes of mitochondrial DNA does not support the monophyly of species within each of the 'lalandii' and 'frontalis' subgroups of Jasus; the subgroupings may need revision. The recently described species J. caveorum is most closely related to J. tristani and J. paulensis, and not to J. frontalis with which it shares an eastern South Pacific distribution and morphological similarity. Two species, J. tristani and J. paulensis, are so genetically similar that further genetic, morphological and behavioural analyses are needed to assess their status as separate species.