BACKGROUND: Iron deficiency is one of the commonest nutritional diseases in young children, which influences cognitive performance and motor development. For the diagnosis of iron deficiency in infants, we evaluated several parameters obtained during the test of routine complete blood count. METHODS: A total of 192 full-term infants were studied. They were aged from 6 to 12 months, who visited Boramae Hospital from Aug 2002 to Oct 2004 according to their routine check up schedules. Venous blood was drawn to determine hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin, hemoglobin content (CH), hemoglobin content of reticulocyte and red cell distribution width (RDW) using ADVIA 120 (Bayer Diagnostics, NY, USA). For iron status, iron, total iron binding capacity and ferritin were determined. The normal, iron deficiency, and iron deficiency anemia groups were defined on the basis of Hb level of 11 g/dL, transferrin saturation of 20%, and/or ferritin level of 12 microgram/L. RESULTS: The significant predictors of iron deficiency state were CH (P<0.001) and RDW (P=0.035). Infants with CH < or = 26 pg could be diagnosed as having an iron deficiency state with 80% sensitivity and 86% specificity. CONCLUSIONS: CH can be used as a new parameter to diagnose an iron deficiency state in infants with the advantage of cost saving and avoiding additional blood sampling. However the reference range should be established before clinical testings and the parameter should be generalized to other automatic analyzers.