Hemoglobin A2 levels in members of an African American family with -88 C-->T beta(+)-thalassemia were measured, and two patients in whom iron deficiency anemia developed were evaluated during treatment. Iron deficiency may diminish the level of HbA2 in healthy control subjects and in patients with heterozygous beta-thalassemia; in addition, it may reduce the amount of variant hemoglobin in certain hemoglobinopathies. Although iron deficiency appeared to be associated with a reduction in HbA2 quantity in the patient with heterozygous beta-thalassemia, the level of HbA2 did not fall below the range characteristic of beta-thalassemia. It had been proposed that mutations in the beta-globin gene promoter may be associated with higher-than-expected levels of HbA2. However, this "mild" beta-globin gene promoter mutation did not seem to result in HbA2 concentrations higher than anticipated in the heterozygous beta-thalassemias.