Oxidative coupling of methane (OCM) was studied with dense tubular Bi1.5Y0.3Sm0.2O3 (BYS) membranes at various temperatures (870 - 930degreesC). BYS powders were synthesized by a citrate method. Tubular-shaped dense membranes of BYS in the fluorite-type FCC phase structure were fabricated by cold isostatic pressing with green machining. The best one-pass C-2 (C2H4 + C2H6) yield achieved for OCM in the BYS dead-end membrane reactor was 35% at a C-2 selectivity of 54% at 900degreesC At the same C-2 yield, the membrane reactor mode gives C-2 selectivity of over 200% higher than the cofeed mode in the same membrane reactor under similar conditions. The oxygen permeation fluxes through tubular BYS membrane reactors under OCM reaction conditions are approximately 1.5 to 3.5 times higher than those under oxygen permeation conditions with He as the purge. After 6 days of OCM, BYS membrane remained in good integrity with minor phase segregation observed at the reaction side of the membrane.