The distribution of b-globin cluster haplotypes has been studied in the populations of Corsica (France) and Sardinia (Italy). The analysis was carried out using five restriction fragment length polymorphism markers on chromosome 11 inside the b-globin cluster using the restriction enzymes HincII and HindIII. The results show a remarkable heterogeneity within the two islands. However, the presence of rare haplotypes common to the most conservative areas (Nuoro and Corte) of the two islands is particularly interesting. These data support the hypothesis of a common origin of the populations of Sardinia and Corsica during the middle and upper Paleolithic periods and could be interpreted as a founder effect.