Six Y-chromosome linked microsatellites were typed in a sample of 135 unrelated males representing three different ethnic groups: Arabs, Berbers and Blacks of Jerba Island (Tunisia). Analysis of variation at the six Y chromosome STRs showed significant differences in allele distributions between the Black group and the two other Islander groups. The Black group revealed the highest level of genetic diversity as compared to Arabs and Berbers, while the latter group was the most homogenous. Allele frequencies obtained for the three islander groups analysed were compared to data available for some European, Mediterranean and African populations. Principal-coordinate analyses showed genetic differentiation between the three geographically closed groups of Jerba. The absence of the YAP insertion marker and the position of Arabs and Jerban Blacks near the European cluster would suggest their relative ‘admixture’ with European populations.