Interest in the study of the effect of cation size upon the configuration assumed by a complex anion led to the determination of the crystal structure of LiCuCl₃ • 2H₂O. A unique (Cu₂Cl₆)⁼ dimer ion was discovered in the structure that was determined by conventional X-ray diffraction techniques. These dimer ions are linked together into a zigzag chain by means of long Cu-Cl bonds between the dimers. The chains in any given unit cell of the crystal are related to each other by a two-fold screw axis. Each dimer has two water molecules associated with it through long Cu-O interactions, giving a distorted octahedral array about each copper ion. There are two additional water molecules per dimer ion which are "lattice waters" and which, along with one of the other oxygens and a chlorine ion, form a tetrahedral hole in which the lithium ion is probably located.