This chapter reports and discusses the fundamental information on the transport of uranium by mycelium of arbuscular mycorrhizal (AM) fungi. The monoxenic cultivation system is shown to be convenient to investigate the processes of uptake and translocation of U by AM fungi, as it was already reported for some other elements. The evidence that extraradical AM hyphae can take up U and translocate it toward the host roots is clearly shown. Further research to understand the mechanisms involved and future prospects are also suggested.