To enlarge the knowledge of genetic characteristics of the populations of the three largest islands of the Western Mediterranean--Corsica (France), Sardinia and Sicily (Italy)--the allele distribution of the VNTR APOB 3' locus was studied. A total of 250 individuals was examined. Twelve different alleles were found, with a minimum of 7 alleles in Sicily and a maximum of 9 alleles in the Sardinians from Campidano of Cagliari and Nuorese. The most frequent allele in all the samples is allele 37, followed by allele 35. The allele frequency distribution appears to be bimodal and the expected heterozygosity is not much higher in comparison with other populations. The polymorphic Information Content (PIC) has a value of 0.84. The Fisher exact test, the matrix of the distances and the dendrogram drawn up from it show a certain heterogeneity between the populations of the three islands, a great variability within Sardinia and a certain degree of affinity between Corsica and the north of Sardinia.