SrFeCo0.5Ox asymmetric membranes for oxygen permeation consisting of a thin dense layer and a porous support layer were prepared using a simple method. A given amount of SrFeCo0.5Ox powder was placed in a die, and then a mixture of SrFeCo0.5Ox powder and ethyl cellulose powder was added on top of the SrFeCo0.5Ox powder. The layered powders were pressed into a 13-mm-diameter disk, and calcined at 1423 K. This produced a membrane with a thin dense layer and, through the elimination of the ethyl cellulose, a porous support layer. Oxygen flux through membranes thus produced increased with decreasing dense-layer thickness. The maximum oxygen flux through an asymmetric membrane at 1173 K observed was 0.23 cm(3) (STP) cm(-2) min(-1), which was 2.8 times larger than that through a 0.95-mm-thick symmetric membrane. Oxygen permeation was primarily limited by bulk diffusion in the thin dense layer, although the porous support layer acted to resist oxygen permeation.