Compression seals based on metal/mica composites were investigated under solid oxide fuel cell (SOFC) operating conditions. Since a compressive force has to be permanently applied in this sealing concept, the mechanical properties of the sealing materials and the SOFC components also became important for maintaining gas tightness. Leakage tests with a sandwich arrangement of mica paper and embossed metallic profiles show leak rates of <1 x 10(-4) mbar l/mm s under an applied normalized compressive load of 2.7 N/mm (0.7 MPa). Also under thermal cycles between ambient temperature and 800degreesC this leak rate does not change due to the elastic response of the seal. Compression tests with the seals in contact with SOFC membranes reveal no damage to the membranes. First results of leakage tests with SOFC stacks are presented, which may serve as a reference for future leakage tests of alternative sealing systems. (C) 2004 Elsevier B.V. All rights reserved.