Dietary iron is present in food both in inorganic forms as ferrous and ferric compounds, and in organic forms, the most important of these being heme iron. The purpose of this review is to evaluate the contributions of both heme and nonheme iron in establishing and maintaining a healthful iron status. The human requirement for iron, bioavailability of heme and nonheme iron, and amounts of heme and nonheme iron in the diet are individually estimated after reviewing the relevant literature in Sections II, III, and IV, respectively. In Section V, the contribution of heme and nonheme iron to human nutrition, as compared to the human requirement for iron (Section II), is estimated after attenuating the amounts of heme and nonheme iron found in the diet (Section IV) by their bioavailabilities (Section III).