A 9-year-old female patient with Imerslund-Gräsbeck syndrome and heterozygosity for beta-thalassemia is presented. At admission the hemoglobin (Hb) was 7.2 g/dL; reticulocytes, 0.2%; red blood cell count (RBC), 2.3 x 10(12)/L; mean corpuscular volume (MCV), 80 fL; hemoglobin A2 (HbA2), 4.3%; fetal hemoglobin intervening sequence (IVS) (HbF), 1.9%. In the bone marrow aspiration smear, megaloblastic changes were observed; the Schilling test was compatible with malabsorption. DNA analysis revealed the presence of heterozygosity for the IVS-I-110 type of beta-thalassemia mutation. Five months after treatment with vitamin B12, Hb was found to be 12.8 g/dL; RBC, 5 x 10(12)/L; MCV, 63 fL.