Four homozygotes for β-thalassemia with normal hemoglobins A2 and F were studied. The absence or scarcity of transfusion requirement and comparatively low hemoglobin F content were the most important findings. Both parents of 3 patients showed the findings of β -thalassemia with normal hemoglobins A2 and F. Biosynthetic studies in 2 patients and their both parents showed moderate or mild β -chain deficiency. The possible reason for this comparatively mild course of a β -thalassemia syndrome lies in a mild deficit in β -chain produc