Transition metals such as Cu, Fe, Mn and Zn are essential micronutrients although when present in excess they can be toxic to cells. The uptake and sequestration of these metals therefore requires careful regulation. Natural resistance associated macrophage proteins (Nramps) have been shown to be involved in transition metal homeostasis and are found in many diverse organisms including bacteria, yeast, mammals and plants. The conservation of these proteins suggests an evolutionary advantage for their role in transition metal transport. Analysis of the AtNramp sequences and comparison to other Nramps suggests that they contain 12 transmembrane domains and a conserved signature motif implicated in transport activity. The tissue-specific expression patterns of the AtNramp genes have been studied using RT-PCR and quantitative PCR performed on root, leaf, stem, flower and silique material. The AtNrampssNere detected in all tissues with the exception of AtNrampS, which was only found in flowers. Upon Fe starvation, AtNramp3 transcript increased in roots while AtNrampd increased in stem. No changes were observed in the other AtNramp genes. The function of the AtNramps has been studied using yeast mutants deficient in Fe uptake. AtNrampS and AtNramp4 were able to rescue the fet3/fet4 Fe uptake mutant while AtNrampS and AtNrampS have not successfully complemented this mutant. Radiolabelled Fe uptake assays in the same cells showed that AtNrampS and AtNramp4 are capable of transporting Fe and that this transport is pH dependent in AtNramp4 transformed cells. A lower level of uptake activity was also observed with AtNrampS in some experiments. Plant lines containing T-DNA inserts within the AtNramp genes have been identified in order to allow the future investigation of the effect of lack of function of the AtNramps. The data presented suggest that members of the AtNramp family play different roles in transition metal homeostasis in Arabidopsis thaliana.