The paper summarizes and discusses the basic properties of solid oxide fuel cell (SOFC) components (electrode materials and electrolyte) from the point of view of their essential functional parameters like chemical stability, transport, catalytic and thermomechanical properties under operational conditions in a SOFC. An interrelation between the defect structure of these materials related to oxygen nonstoichiometry and their electrical properties and catalytic activity was shown. (c) 2007 Elsevier B.V All rights reserved.