Two diabetic patients with unusual high levels of glycosylated hemoglobin measured by dolt exchange chromatography are described. Further studies revealed a persistence of fetal hemoglobin in both cases. This condition produces falsely high levels of glycosylated hemoglobin, when ion exchange chromatography is used. These cases may be overtreated with risk of hypoglycemia. Patients with inappropriate levels of glycosylated hemoglobin should be investigated for hemoglobinopathies.