A gas-tight LSCF hollow fiber membrane that possesses an asymmetric structure has been prepared in a single-step using an immersion induced phase inversion technique. The results obtained from oxygen permeation experiments show that the porous inner surface of the prepared LSCF hollow fiber membrane is favorable for oxygen permeation when the feed air is introduced in the dense outer surfaces of the membranes. (c) 2005 Elsevier B.V.. All rights reserved.