A new layered bismuth tellurium oxychloride, Bi(3)Te(4)O(10)Cl(5) has been synthesized by a solid-state reaction under vacuum using Bi(2)O(3), TeO(2), and TeCl(4) as reagents. The structure of Bi(3)Te(4)O(10)Cl(5) has been determined by single-crystal X-ray diffraction. Bi(3)Te(4)O(10)Cl(5) contains two different lone pair cations, Bi(3+) and Te(4+) that are in asymmetric coordination environments. Bi(3)Te(4)O(10)Cl(5) has a novel two-dimensional layered structure consisting of distorted BiO(4)Cl(2) octahedra, BiO(4)Cl(3) polyhedra, TeO(4) polyhedra, and isolated Cl(-) ions. Complete structural analysis, infrared spectrum, thermogravimetric analysis, and dipole moment calculations are presented. Crystal data: Bi(3)Te(4)O(10)Cl(5), monoclinic, space group C2/m (No. 12), a = 15.372(3) A, b = 4.1004(7) A, c = 13.301(2) A, beta = 98.336(5) degrees, V = 829.5(2) A(3), and Z = 2.