Four new layered mixed-valence vanadium oxides, which contain interlamellar organic cations, alpha-(H3N(CH2)(2)NH3) [V4O10] (1a), beta-(H3N(CH2)(2)NH3)[V4O10] (1b), alpha-(H2N(C2H4)(2)NH2)[V4O10] (2a), and beta-(H2N(C2H4)(2)NH2) [V4O10] (2b), have been prepared under hydrothermal conditions and their single-crystal structures determined : 1a, triclinic, space group , a = 6.602(2) Angstrom, b = 7.638(2) Angstrom, c = 5.984(2) Angstrom, alpha = 109.55(3)degrees, beta 104.749(2)degrees, gamma = 82.31(3)degrees, Z = 1; 1b, triclinic, , a = 6.387(1) Angstrom, b = 7.456(2) Angstrom, c = 6.244(2) Angstrom, alpha = 99.89(2)degrees, beta = 102.91(2)degrees, gamma = 78.74(2)degrees, Z = 1; 2a, triclinic, , a = 6.3958(5) Angstrom, b = 8.182(1) Angstrom, c = 6.3715(7) Angstrom, alpha = 105.913(9)degrees, beta = 104.030(8)degrees, gamma = 94.495(8)degrees, Z = 1; 2b, monoclinic, space group P2(1)/n, a = 9.360(2) Angstrom, b = 6.425(3) Angstrom, c = 10.391(2) Angstrom, beta = 105.83(1)degrees, Z = 2. All four of the compounds contain mixed-valence V5+/V4+ vanadium oxide layers constructed from V5+O4 tetrahedra and pairs of edge-sharing V4+O5 square pyramids with protonated organic amines occupying the interlayer space.