Open-circuit measurements and Li-6 magic-angle spinning (MAS) NMR spectroscopy were used to study Li coordination in partly reduced Li1.1Ti1.9O4 + delta spinels prepared by hydrothermal reaction. The reduced spinels show four different Li sites. Signals at -0.2 and 0.3 ppm correspond to Li in 16d and 8a positions. The signal at 0.9 ppm corresponds to a tetrahedrally coordinated Li and represents the primary site for the inserted lithium. The signal at -0.7 ppm appears simultaneously with a decrease of the population of Li in 8a position and indicates a local phase transition connected with ordering of Li into 16c positions. (C) 2004 The Electrochemical Society.