The alpha-thalassemia mutations in 34 Jewish patients of various origins and in 13 Arab patients have been identified using DNA technologies. Middle Eastern Jews and Arabs have both deletional and nondeletional mutations, but in the former the most frequent mutation is the Mediterranean deletion while in Arabs it is the polyadenylation signal mutation. Another nondeletional mutation, the 5 bp deletion at the IVS1 splice donor site has only been found in Arabs. Yemenite and European Jews have only deletional mutations and the most frequent is the 3.7 kb deletion. A long deletion that involves the two alpha-globin genes, is found only in Yemenis.