Serum ferritin, hemoglobin, serum iron and transferrin iron-binding capacity were evaluated in 107 healthy female students. 21 women had a serum ferritin of 12 µg/l or less, corresponding to an exhaustion of body iron stores. After 1 month of iron supplementation, significant increase of hemoglobin concentration and decrease of total iron-binding capacity were observed. Mean serum ferritin had increased from 24 to 41 µg/l, and all women had a serum ferritin above 12 µg/l. 1 month after the end of the trial, serum ferritin fell significantly. This study points out the problem of serum ferritin reference values and the definition of normal iron stores in menstruating women.