Three orthorhombic crystals of chemical formula Eu
x
V
y
Mo8±z
O14 were investigated by X-ray diffraction (Mo Kα radiation, λ = 0.71073 Å). They have nearly the same lattice parameters (a ≃ 11.3, b ≃ 10.0, c ≃ 9.2 Å), display one-dimensional incommensurate modulations of wavevector q* = γc* and are characterized by the same superspace group Cmca(00γ)s00. The crystals differ both in their compositions (namely Eu0.976(6)V1.13(5)Mo7.10(5)O14, Eu0.986(4)V1.10(3)Mo7.30(1)O14 and EuMo7.96(1)O14) and in their γ components [0.195 (2), 0.245 (2) and 0.286 (3), respectively]. The average structures of these crystals appear closely related to the structures of LaMo7.7O14 (not modulated) and LaMo8O14 (modulated); however, two main differences are outlined: first, the modulation direction is c in the Eu-containing crystals but b in the modulated La-containing crystal [q* = (1/3)b*], second, the Eu-containing crystals have centrosymmetric structures while the La-containing crystals have polar structures (space group C2ca). The Mo (or Mo and V) atoms are stacked to form (001) layers of metallic clusters. The density modulation of these structures implies the existence of the new types of clusters Mo9, Mo10, Mo6V4, Mo7V3 and Mo8V2 besides the clusters M
8 (Mo8, Mo6V2 and Mo7V) and M
7 (Mo7 and Mo6V) which are already known. Mo8 units with cis and trans configurations and Mo6V2 units with a trans configuration appear as the main cluster types in these crystals. The nature of the metallic clusters changes along c, but inside one (001) layer it is likely that only one cluster type with a given configuration is present. The main structural result is the formation, in some unit cells, of strong intercluster Mo—Mo, Mo—V or V—V bonds with distances close to 2.6 Å within a layer as well as between two neighbouring layers.