Iron deficiency, the most common nutritional deficiency worldwide, has negative effects on work capacity and on motor and mental development in infants, children, and adolescents, and maternal iron deficiency anemia might cause low birthweight and preterm delivery. Although iron deficiency is more common in developing countries, a significant prevalence was observed in the United States during the early 1990s among certain populations, such as toddlers and females of childbearing age. One of the national health objectives for 2010 is to reduce iron deficiency in these vulnerable populations by 3-4 percentage points (objective no. 19-12). CDC has published recommendations to prevent iron deficiency in the United States. To characterize the iron status of persons in the United States, CDC calculated the prevalence of iron deficiency and iron deficiency anemia by applying a multiple-indicator model to data from the 1999-2000 National Health and Nutrition Examination Survey (NHANES 1999-2000). These values were compared with those observed in the third National Health and Nutrition Examination Survey (NHANES III [1988-1994]) using the same multiple-indicator model. This report summarizes the results of this analysis, which indicate that iron deficiency remains 2-5 percentage points above the 2010 national health objectives. To prevent iron deficiency, vulnerable populations should be encouraged to eat iron-rich foods and breast-feed or use iron-fortified formula for infants.