The electrophoretic polymorphism of the PGP locus has been studied in about 1,700 Italians. The sample consisted of individuals from Viareggio (North-Central Italy), Rome (Central Italy) and Cagliari (Sardinia, Southern Italy). Comparison among the three groups showed a high degree of heterogeneity. The Sardinian sample was well differentiated from the other two concerning the frequencies of both the PGP3 and of PGP2 alleles. The frequency of the PGP1 allele varied from 0.900 (Viareggio) to 0.987 (Cagliari). The gene frequencies, together with those available for other European populations were plotted against the latitudes of the different localities sampled and fitted to a North-South cline.