Helleria brevicornis is with no doubt a very intriguing organism. lts peculiar morphological features clearly separate this species from the rest of Oniscidea. Even attempts at reconstructing its phylogenetic position by using mithochondrial DNA molecular data were largely unsuccessful, mainly because of some peculiarities of its mitochondrial genome (Michei-Salzat and Bouchon, 2000). The Tyrrenianan distribution of this species is an additional interesting issue. Distributed in two of the three major islands of the West Mediterranean Sea, Sardinia and Corsica, Helleria also occurs spottily in few continental areas of the Thyrrenian basin (France, ltaly), and some, but not all, islands of the Tuscanian Archipelago. The biogeography and the supposed ancient evolutionary history of this species provide ground for hypothesizing that the present geographic distribution could be a remnant of a once larger one, and that the paleogeographic events that led to the formation of the Sardinia-Corsica plate, datable back to the Oligocene, could be reflected in the present geographic distribution of this species. To address this issue, we investigated the phylogeography of Helleria brevicornis by sequencing approximately 1.4 Kb of the mtDNA (16S, 12S, and COI) in more than 50 individuals from 20 different populations. Taxonomic implications of the results obtained are also discussed.