The hydrothermal chemistry of the CsVO3/methylenediphosphonate system was investigated. Variations in reaction temperatures, heating times, and stoichiometries of reactants resulted in the isolation of mononuclear, one-, two-, and three-dimensional species : Cs[VO(HO3PCH2PO3H)(2)(H2O)] (1), Cs[VO(HO3PCH2PO3)] (2), Cs[(VO)(2)V (O-3-PCH2PO3)(2)(H2O)(2)] (3), and [V(HO3PCH2PO3)(H2O)] (4), respectively. The structure of the anion of 1 consists of isolated V(IV) octahedra. Phase 2 adopts a chain structure constructed from corner-sharing V(IV) octahedra, forming infinite {-V=OV=O-} linkages. The layer structure of 3 contains trinuclear units of corner-sharing {VO6} octahedra with the central V site in the III oxidation state and V(IV) centers at the extremities of the cluster. The diphosphonate ligands serve to link neighboring trinuclear motifs into a layer structure three octahedra in depth. The Cs+ cations occupy cavities within the lavers, rather than the more common interlamellar positions. The structure of 4 consists of isolated {V(III)O-6} octahedra linked by diphosphonate groups into a three-dimensional framework. Crystal data : for 1, CH6O7P2V0.5Cs, monoclinic C2, a = 10.991(2) Angstrom, b = 10.161(2) Angstrom, c = 7.445(1) Angstrom, beta = 92.97(3)degrees, Z = 4; for 2, CH3O7P2VCs, monoclinic C2, a = 10.212(2) Angstrom, b = 10.556(2) Angstrom, c = 14.699(3) Angstrom, beta = 94.57(2)degrees, Z = 8; for 3, C2H8O16P4V3Cs, monoclinic C2/m, n = 9.724(2) Angstrom, b = 8.136(2) Angstrom, c = 10.268(2) Angstrom, beta = 103.75(3)degrees, Z = 2; for 4, CH5O7P2V, monoclinic P2(1)/n, a = 5.341(1) Angstrom, b = 11.515(2)Angstrom, c = 10.558(2) Angstrom, beta = 99.89(1)degrees, Z = 4.