The title compound, lithium magnesium chloride heptahydrate, LiCl.MgCl(2).7H(2)O, was analyzed in 1988 by powder X-ray diffraction [Emons, Brand, Pohl & Köhnke (1988). Z. Anorg. Allg. Chem. 563, 180-184] and a monoclinic crystal lattice was determined. In the present work, the structure was solved from single-crystal diffraction data. A trigonal structure was found, exhibiting a network structure of Mg(H(2)O)(6) octahedra and Li(H(2)O)Cl(3) tetrahedra connected by H...Cl hydrogen bonds. The [Li(H(2)O)](+) unit is coordinated by distorted edge-connected Cl(-) octahedra.