Nine-hundred and twenty-two individuals belonging to the five provinces of Puglia were typed for nine erythrocyte genetic markers (ACP1, ADA, AK1, ESD, GLO1, PGD, PGM1, PGM2, and SODA). Genetic heterogeneity within Puglia was investigated on the basis of allele frequencies of the above mentioned markers plus ABO*A, ABO*B, ABO*O, and RH*D, by the (chi 2 test and Rst statistic. The analyses revealed no differences at the provincial level. Furthermore, correspondence and genetic distance analyses were applied to look for a statistical difference within Puglia from different standpoints, as well as between Puglia, the rest of Italy and other European and Near and Middle Eastern populations whose genetic history is most likely related. Southern and central Italian, Greek and Aegean populations appeared very homogeneous and quite differentiated from the rest of Europe, both continental (including northern Italy) and south-eastern, stressing the major impact of the heavy Greek colonization on the genetic pools of the circum-Mediterranean people.