The garnet-related oxide with nominal formula Li7La3Zr2O12 prepared by the sol–gel method is cubic, space group Ia-3d with lattice parameter a =12.9720Å at room temperature. The occupancies of three lithium positions (24d, 48g, 96h) and the position of a small amount of Al3+ (ca 0.61wt%) inside the grains were determined by neutron diffraction. The occupancy of the 24d Li sites was reduced to 36.0% by the Al3+ occupying the 48g sites. The bulk and total Li+-ion conductivity at 25°C was 3.1×10−4 Scm−1 and 1.4×10−4 Scm−1 with an activation energy 0.34eV in the temperature range 25–160°C.