A mechanochemically assisted method for synthesizing spinel Li4Mn5O12 has been proposed in this paper. The method involves grinding a mixture of LiOH.H2O and gamma-MnO2 in ambient air, followed by heating the ground product. The grinding of the mixture was conducted by using a planetary ball mill, causing their structural changes into amorphous state, which is lithium manganese oxides hydrated (Li-MnO.nH(2)O). The ground product can be crystallized into lithium manganese oxide by heating at about 400 degreesC or more. Heating the ground product at around 600 degreesC for 12 h results in the formation of pure phase of the spinel. Temperature in the heating stage is an important factor in crystallization of the spinel from the amorphous mixture, and heating up to about 600 degreesC is suitable for the formation of pure phase spinel. The product synthesized is very fine powder with mean grain size of 100 nm. (C) 2003 Elsevier Science B.V. All rights reserved.