The task of the iron regulatory system is to balance between iron-stores and iron-consumption. Recently the predominant negative regulator of iron absorbtion in the small intestine and iron release from macrophages has been discovered. That is the hepcidin. Hepcidin, the 25-amino acid peptide produced by the hepatocytes, may be a new mediator of innate immunity and the long-sought iron regulatory hormone. Hepcidin is an acute phase peptide, its production is increased in inflammation and in iron overload. According to evidence obtained in mouse models hepcidin decreases the iron absorbtion in the small intestine and inhibits iron release from macrophage and iron transport across placenta. Hereby the hepcidin decreases the plasma iron level. The exact patomechanism of hepcidin is not clarified and its receptor is still unknown. The discovery of hepcidin and its role in iron metabolism could lead to new diagnostic possibilities on the field of hemochromatosis, other iron-regulatory diseases and anaemia of inflammation.