The reactions of UO3 with acidic aqueous chloride solutions resulted in the formation of two new polymeric U(VI) compounds. Single crystals Of Cs-2[(UO2)(3)Cl-2(IO3)(OH)O-2].2H(2)O (1) were formed under hydrothermal conditions with HlO(3) and CsCl, and Li(H2O)(2)[(UO2)(2)Cl-3(O)(H2O)] (2) was obtained from acidic LiCl solutions under ambient temperature and pressure. Both compounds contain pentagonal bipyramidal coordination of the uranyl dication, UO22+. The structure of 1 consists of infinite [(UO2)(3)Cl-2(IO3)(mu(3)-OH)(mu(3)-O)(2)](2-) ribbons that run down the b axis that are formed from edge-sharing pentagonal bipyramidal [UO6Cl] and [UO5Cl2] units. The Cs+ cations separate the chains from one another and form long ionic contacts with terminal oxygen atoms from iodate ligands, uranyl oxygen atoms, water molecules, and chloride anions. In 2, edge-sharing [UO3Cl4] and [UO5Cl2] units build up tetranuclear [(UO2)(4)(mu-Cl)(6)(mu(3)-O)(2)(H2O)(2)](2-) anions that are bridged by chloride to form one-dimensional chains. These chains are connected in a complex network of hydrogen bonds and interactions of uranyl oxygen atoms with Li+ cations. Crystal data: 1, orthorhombic, space group Prima, a = 8.2762(4) Angstrom, b = 12.4809(6) Angstrom, c 17.1297(8) Angstrom, Z = 4; 2, triclinic, space group P (1) over bar, a = 8.110(1) Angstrom, b = 8.621 (1) Angstrom, c = 8.740(1) Angstrom, Z = 2.