Two ways of reverse micelle (RM) method were investigated to prepare carbon-supported nano-sized LaMnO3 with high oxygen reduction activity. Hydrolysis precipitation in reverse micelle (HP-RM) method could give nano-sized particles of LaMnO3 easily because the particles size decreased with decreasing R-w (=[H2O]/[surfactant]) value as well as nitrate concentration. The electrode prepared by the resulting particles showed high oxygen reduction activity as compared with that prepared by mechanical mixing-method. Furthermore, it was found that new RM method (ROP-RM) using KMnO4 as an oxidizer gave higher oxygen reduction activity than the HP-RM method, although particle size of LaMnO3 obtained by the ROP-RM method was almost same as that by RM-HP method. (C) 2007 Published by Elsevier B.V.