The dense dual phase composite membrane made from strontium-stabilized bismuth oxide and silver, (Bi2O3)(0.74)(SrO)(0.26)-Ag (40% v/o), was investigated. The composite was found to exhibit very high electrical conductivity at the room temperature, revealing that the silver phase has formed electron-conducting networks in the oxide matrix. The composite shows much improved oxygen permeability compared with the bismuth oxide alone. An oxygen flux of 5 x 10(-8) mol cm(-2) s(-1) was observed for a 1.00 mm thick composite at 700 degreesC with oxygen partial pressures of the feed and permeate side at 0.209, 0.0024 atm, respectively. Combination of electrical conductivity and oxygen permeation measurements reveals that oxygen-ion conduction through the oxide phase of the composite is the rate-limiting step for oxygen permeation.