La 2NiO 4 tubular membranes of relative density over 92% were used to separate oxygen from air and facilitate the partial oxidation of methane to H 2 and CO at 900 °C. When methane was fed into a tube of inner surface area 5.11 cm 2 at a rate of 10.5 ml/min, methane throughput conversion was 89%, CO selectivity 96%, H 2/CO ratio 1.5, and the equivalent oxygen flux was 6.8 ml/min. The surface of the La 2NiO 4 membrane exposed to CH 4 decomposed into La 2O 3 and Ni, while the surface in contact with air remained almost unchanged. It is suggested that the conversion of methane in the membrane reactor involves the reforming of methane by the H 2O and CO 2 catalyzed by nickel.