Large (5-9 cm in length) land snails of the genus Placostylus are found in New Caledonia and the Loyalty Islands, northern New Zealand, the Three Kings Islands just north of New Zealand and on Lord Howe Island. Their presence on Lord Howe, an oceanic island less than 6 million years old, has been an intriguing biogeographical question. Maximum parsimony and maximum likelihood analyses using cytochrome c oxidase subunit I sequence data suggest that the Lord Howe Island and mainland New Zealand taxa are sisters, but that the Three Kings taxon is independently derived, possibly from New Caledonian stock. Placostylus colonies throughout the area of the present study are under considerable threat, with many intraspecific forms and some species threatened and some listed as endangered species. The taxonomic and conservation status of the Lord Howe Island populations are discussed.