The new compound Sm3NbO4S3 was obtained and its structure was determined by single crystal X-ray diffraction. The following crystal data were obtained: M-r = 704.14 g.mol(-1), orthorhombic symmetry with unit cell parameters a = 6.6890(13), b = 7.6630(15), and c = 14.216(3) Angstrom, space group Pn2(1)a (No. 33). Refinement from 2447 unique reflections with I > 2 sigma (I), and 101 variables, converged to the reliability factor R = 2..46%. Two different types of polyhedra can be distinguished: a bicapped trigonal prism around Sm2 and Sm22, and a very distorted prism with eight surrounding atoms (four O and four S atoms) around Sm1 and Nb1. (C) 2000 Elsevier Science Ltd. All rights reserved.