Recent advances in cloning of proteins involved in intestinal iron absorption can inform design and understanding of therapeutic iron preparations. Redox chemistry of iron is particularly important in iron metabolism, both as a potential source of toxic intermediates and as an essential requirement for efficient iron transport. The initial step in iron absorption (uptake from lumen to mucosa) is particularly important and several pathways involving Fe(III) reduction or transport and Fe(II) transport have been identified. Novel genes associated with iron uptake include Dcytb, a putative iron-regulated reductase and DMT1, a Fe(II) carrier in the brush border membrane. Other mechanisms may also operate, however. We review the recent findings and apply this to understanding the absorption of Fe(III) pharmaceuticals.