Mild iron deficiency is common among infants, adolescents and women during the childbearing years. Practical and economical approaches toward its identification, treatment and prevention are needed. Laboratory screening is based on hemoglobin or hematocrit determinations compared with age-specific and sex-specific reference standards. If blood specimens have been analyzed by electronic counter, the presence of a normal or low-normal value for red cell volume increases the likelihood that anemia is due to iron deficiency. Other laboratory tests that may be helpful in selected cases include determining serum ferritin, transferrin saturation or erythrocyte protoporphyrin values. However, in most cases, a simple therapeutic trial with ferrous sulfate may be instituted on the basis of history and a screening test alone. If repeat laboratory studies after a month show no improvement, iron treatment should be stopped and other causes of anemia should be considered.