A series of perovskite-type manganites, LnMnO(3) (Ln = lanthanoids or Y), were examined for their electrode-catalytic activities to reduce oxygen in alkaline solution. Polarization experiments using gas diffusion-type electrodes revealed that the catalytic activity differed significantly with a change in Ln, being in the order of La > Pr > Nd > Sm > Gd > Y > Dy > Yb. This order coincides with the decreasing order of the ionic radius of La3+.