The reactions of HgS and HgSe with HgI 2 yield Hg 3 S 2 I 2 and Hg 3 Se 2 I 2 , respectively. Orange crystals of Hg 3 S 2 I 2 and light red crystals of Hg 3 Se 2 I 2 are formed in evacuated glass ampoules at 2603C in yields of 50% as the only crystalline compounds. The crystal structures have been solved and re5ned to R β«Ψβ¬ 0.0449, wR (F 2 ) β«Ψβ¬ 0.0751 for Hg 3 S 2 I 2 and R β«Ψβ¬ 0.0518, wR (F 2 ) β«Ψβ¬ 0.0993 for Hg 3 Se 2 I 2 on the basis of single-crystal X-ray di4raction data. Both compounds are isotypic and crystallize in the orthorhombic space group Imma with Z β«Ψβ¬ 8. The lattice constants are a β«Ψβ¬ 979.92(8) pm, b β«Ψβ¬ 1870.3(3) pm, c β«Ψβ¬ 946.22(7) pm for Hg 3 S 2 I 2 and a β«Ψβ¬ 976.60(9) pm, b β«Ψβ¬ 1938.1(3) pm, c β«Ψβ¬ 963.32(9) pm for Hg 3 Se 2 I 2 . The structures contain one-dimensional polycationic folded bands (Hg 3 E 2 ) 2Ψ (E β«Ψβ¬ S, Se) with intercalated I Ψ ions. Alternatively, the polycationic part can be described as trigonal Hg 3 E pyramids which are interconnected in the way that they form one-dimensional channels. Discrete iodide ions separate these cationic channels.