In six Jewish populations from Eastern, Central and Southern Europe, the Middle East, North Africa and Yemen, the frequencies of 30 genes from 13 loci were determined. The calculation of genetic distances between these populations as well as a cluster analysis were done. The gene frequencies of these six populations were computed together with those of 19 other Jewish populations of diverse countries described in the literature. Of the 19 populations, 22 alleles from 10 loci were checked. Gene frequencies in autochthonous, non-Jewish populations from these countries were also computed. All Jewish populations except Yemenites are concentrated in the same cluster, being closer one to another than to any of the non-Jewish groups. A similar picture is obtained when Jewish and non-Jewish populations from 19 countries are subjected to cluster analysis. The differences between the Jewish populations generally tend to bring them closer to the corresponding non-Jewish groups. The present data suggest that these differences cannot always be explained by admixture; other factors such as the effect of convergent adaptive processes must be considered.