Within the framework of the Italian research project TUNING dealing with the characterization of the spatial and temporal patterns of genetic variation in the Mediterranean tunas and coordinated by the University of Bologna, we tried to reconstruct the demographic history and short-term temporal changes of genetic diversity in the Atlantic bluefin tuna (Thunnus thynnus) of the Mediterranean Sea. Bluefin tuna is experiencing a period of strong overfishing reflected by the lowering of mean age and size of catches, and FAO and ICCAT are adopting measures to recover this species. The comparative study of genetic diversity and genetic differentiation in historical (1900-1930) and contemporary (1999-2007) samples of Atlantic bluefin tuna sampled in the last 100 years in the Western and Central Mediterranean offered the opportunity to assess the impact of industrial fishery on the genetic variation of the stock. Genetic composition of tuna samples at 9 microsatellite loci was dissected by using several programs (Microsatellite, GENETIX 4.05, Arlequin3.01, FSTAT 2.9.3, MNE2, tm3, M_P_VAL, Bottleneck) to detect spatial and temporal changes in the population genetic parameters (gene diversity, genetic differentiation among population samples, effective population size) and to estimate the role of environmental (natural and anthropogenic) factors affecting genetic variation. Significant, if limited spatial heterogeneity was detected across all modern samples (Fst= 0.03, P< 0,0001) as well as significant genetic differentiation between north and south Thyrrenian Sea, and between Adriatic and Thyrrenian Sea. No decrease of genetic variation was observed in modern samples with respect to the ancient one. Both temporal and onesample methods agree that the effective population size is low with respect to comparable Theleost species (Ne= 1000-2000). The two methods we used to detect a bottleneck event had discordant results, with only one (M_P_VAL) clearly detecting a bottleneck. Because only dramatic reductions of population size in a short period result in a detectable signal for the software of Cornuet et al. these results do not rule out the possibility of a demographic decline. Rather they show that, if there was a decline, it was not drastic enough to erase a substancial fraction of DNA diversity, which did not apparently change in the last century.