A single crystal of LiMn2O4 (similar to 35 X 20 X 12 mum) was prepared by a flux method. The electrochemical properties of this material were investigated in a 1 M LiClO4/propylene carbonate + ethylene carbonate solution using a microelectrode technique. A Pt microfilament was brought into contact with the single crystal, and cyclic voltammetry and potential step chronoamperometry measurements were successfully performed on this electrode. The single crystal of LiMn2O4 exhibited reversible behavior during the Li-ion extraction/insertion. A new peak was observed at 3.86 V vs. Li/Li+ which was not clearly reported so far on polycrystalline of LiMn2O4. The chemical diffusion coefficient of Li-ion into the LiMn2O4 crystal was estimated to be 10(-11) cm(2)/s.