Thalassemias are genetically heterogeneous group of disorders with reduced or absent production of globin. β-Thalassemia major can be caused by homozygosity or compound heterozygosity for β-globin gene mutation. Here we report, for the first time in Turkey, three cases who carry the nonsense β-thalassemia (β-thal) mutation at codon 37 (TGG>TGA; Trp→Stop) causing premature stop codon.