Heterozygosity for β-thalassemia is usually characterized by hypochromia, microcytosis, mild anemia, an increased percentage of Hb A2, and normal or mildly increased Hb F. We have studied an unusual type of β-thalassemia with typical morphologic abnormalities but normal levels of Hb A2and Hb F, with diagnosis confirmed by globin synthesis studies. The results indicate that globin synthesis studies may be necessary when the cause of hypochromia and microcytosis cannot be clearly determined by hemoglobin quantitation and electrophoresis and other standard clinical tests.β-Thalassemia minor is usually characterized by hypochromia, microcytosis and an elevated percentage of hemoglobin A2(Hb A2). Fetal hemoglobin levels may also be slightly elevated in about half of affected persons.(1)β-Thalassemia minor with hypochromia, microcytosis, and normal levels of Hb A2and Hb F has occasionally been described, but documentation of the diagnosis has generally not been precise. We wish to report two heterozygotes of this type in whom the diagnosis has been confirmed by globin synthesis studies.