The crystal structure determination of two new oxychalcogenides, namely Eu5V3S6O7 and La10Se14O, is reported. Eu5V3S6O7 crystallizes in the orthorhombic symmetry (space group Pmmn) with unit cell parameters (in Angstrom): a = 17.463(2), b = 3.6732(4), and c = 10.007(1). This compound is isotypic with the Ln(5)V(3)S(6)O(7) compounds (Ln = La-Nd), and its structure has been refined to R1 = 0.0248. Eu atoms, which are nine-coordinated by O and S atoms, are associated to form ribbons that are interconnected by [VS4O2] octahedrons. La10Se14O crystallizes in the tetragonal symmetry (space group 14(1)/acd) with unit cell parameters (in Angstrom): a = 15.926(2), and c = 21.061(5). The structure was refined to R1 = 0.0347. La10Se14O is isostructural with the Pr10X14O compounds (X = S and Se). The only structure difference is observed for one La site that is found split, in connection with a mixed O/Se site filling. (C) 2002 Elsevier Science Ltd. All rights reserved.