The sulfates Nb2O2(SO4)(3), MoO2(SO4), WO(SO4)(2), and two modifications of Re2O5(SO4)(2) have been synthesized by the solvothermal reaction of NbCl5, WOCl4, Re2O7(H2O)(2), and MoO3 with sulfuric acid/SO3 mixtures at temperatures between 200 and 300 degrees C. Besides the X-ray crystal structure determination of all compounds, the thermal behavior was investigated using thermogravimetric studies. WO(SO4)(2) (monoclinic, P2(1)/n, a = 7.453(1) angstrom, b = 11.8232(8) angstrom, c = 7.881(1) angstrom, beta = 0.107.92(2)degrees, V = 660.7(1) angstrom(3), Z = 4) and both modifications of Re2O5(SO4)(2) (I: orthorhombic, Pba2, a = 9.649(1) angstrom, b = 8.4260(8) angstrom, c = 5.9075(7) angstrom, V = 480.27(9) angstrom(3), Z = 2; II: orthorhombic, Pbcm, a = 7.1544(3) angstrom, b = 7.1619(3) angstrom, c = 16.8551(7) angstrom, V = 863.64(6) angstrom(3), Z = 4) are the first structurally characterized examples of tungsten and rhenium oxide sulfates. Their crystal structure contains layers of sutfate connected [W=O] moieties or [Re2O5] units, respectively. The cohesion between layers is realized through weak M-O contacts (343-380 pm). Nb2O2(SO4)(3) (orthorhombic, Pna2(1), a = 9.9589(7) angstrom, b = 11.7983(7) angstrom, c = 8.6065(5) angstrom, V = 1011.3(1) angstrom(3), Z = 4) represents a new sulfate-richer niobium oxide sulfate. The crystal structure contains a three-dimensional network of sulfate connected [Nb=O] moieties. In MoO2(SO4) (monoclinic, l2/a, a = 8.5922(6) angstrom, b = 12.2951(6) angstrom, c = 25.671(2) angstrom, beta = 94.567(9)degrees, V = 2703.4(3) angstrom(3), Z = 24) [MoO2] units are connected through sulfate ions to a three-dimensional network, which is pervaded by channels along [100] accommodating the terminal oxide ligands. In all compounds except WO(SO4)(2), the metal ions are octahedrally coordinated by monodentate sulfate ions and oxide ligands forming short M=O bonds. In WO(SO4)(2), the oxide ligand and two monodentate and two bidentate sulfate ions build a pentagonal bipyramid around W. The thermal stability of the sulfates decreases in the order Nb > Mo > W > Re; the residues formed during the decomposition are the corresponding oxides.