Hereditary atransferrinemia is a very rare disorder characterized by microcytic anemia and iron overload. It has been reported in only 10 patients in 8 families. The molecular basis of atransferrinemia has been determined in only 3 human cases. We now report a new patient with this rare disorder, who is the first known case in Turkey, the 11th patient reported in the published literature and only the 4th case of human atransferrinemia characterized on a molecular basis. DNA analysis of the serum transferrin gene in the patient revealed a previously undescribed mutation in exon 4, a G→A transition at cDNA 410(Cys137Tyr). A number of previously known polymorphisms and a previously undescribed mutation at IVS10(–23)C→T, presumably a polymorphism, were also documented.