In our investigation of rare earth sulfides in the AE-RE-Sn-S (AE=alkaline-earth, RE=rare earth) system, three isostructural quaternary sulfides have been obtained. These compounds adopt the Eu 5 Zr 3 S 12 structure type and crystallize in the P-62m space group (no. 189); the crystal data are as follows: Sr 2 Y 2.67 Sn 3 S 12 , a=11.600(7)Å, c=3.948(3)Å, Z=1; Ca 3 La 2 Sn 3 S 12 , a=11.5997(6)Å, c=3.9407(4)Å, Z=1; Ca 3 Er 2 Sn 3 S 12 , a=11.448(3)Å, c=3.8780(11)Å, Z=1. Single-crystal analysis indicated that the crystal structures consist of three types of building block: RES 7 , AES 6 , and SnS 6 units. The structure of Sr 2 Y 2.67 Sn 3 S 12 is characterized by the [Y3S(1)12/2S(2)3S(3)3]1∞ trimer-chains along the c direction, which are connected into a 3-dimensional framework by the Sn atoms via S(1), S(2), and S(3), with Sr atoms filling in the channels along the c direction. The optical band gap of 1.45eV for Ca 3 La 2 Sn 3 S 12 was deduced from the diffuse reflectance spectrum.