Key-words:Austropotamobius italicus was once widely distributed throughout most of the country's limestone basins in Spain. But its populations have shown a very strong decline over the last thirty years, due to different factors. Thus, the species now enjoys protection under regional, national and international legislation. Therefore, knowledge of the levels and patterns of distribution of genetic diversity in crayfish populations is critical when making conservation management decisions. In the present work, the current genetic structure of Spanish populations of white-clawed crayfish, A. italicus, was analyzed. Eleven Spanish populations and an Italian sample were studied through an 1184 bp-lentgh sequence of cytochrome oxidase subunit I mitochondrial gene. Data analysis revealed the existence of eight haplotypes in the Iberian Peninsula, the highest diversity reported to date in Spanish crayfish. Also a substantial genetic differentiation among populations was found, with a clear geographic pattern. The genetic variability found in these populations is similar to, and even higher, than that reported in previous studies on other Spanish and European populations of A. italicus. Thus, given the current risk status of the species across its range, this variability in certain populations offers some hope for the species from a management point of view. RÉSUMÉ La variabilité de l'ADN mitochondrial des populations espagnoles d' A. italicus déduite de l'analyse d'une région COI Mots-clés :Austropotamobius italicus, mtDNA, Austropotamobius italicus était autrefois largement distribué dans la plupart des régions des bassins calcaires en Espagne. Mais ces populations ont montré une baisse très forte au cours des trente dernières années, en raison de différents facteurs. Ainsi, l'espèce bénéficie aujourd'hui d'une protection législative régionale, nationale et internationale. Par conséquent, la connaissance des niveaux et des schémas de distribution de la diversité des ressources génétiques dans les populations d'écrevisses est essentielle pour prendre des décisions de bioconservation. Dans le présent travail, la structure génétique actuelle des populations espagnoles de l'écrevisse à pattes blanches, A. italicus, a été analysée. Onze populations