Perovskite hollow fibre membranes of the composition BaCoxFeyZr1-x-yO3-delta (BCFZ) were prepared by a spinning process and subsequent sintering. The fibres were successfully tested in the production of pure oxygen and oxygen-enriched air as well as in a catalytic membrane reactor for the partial oxidation of methane to synthesis gas. In addition to BCFZ, for comparison perovskites of the composition Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) and Ba0.5Sr0.5Zn0.2Fe0.8O3-delta (BSZF) as well as SrCo0.8Fe0.2O3-delta (SCF) were prepared and tested. The atomic structure of the grain boundaries and their influence on oxygen transport are discussed. The thermal expansion coefficient is derived from in situ high temperature XRD. (c) 2006 Elsevier B.V. All rights reserved.