A fuel cell stack (2) comprises a stack (3) of alternating solid oxide fuel cell and gas separator plates within a housing (4). Each fuel cell plate has apertures therethough aligned with corresponding apertures through adjacent separator plates. A first aligned series of apertures in the fuel cell and separator plates opens to the anode side of each fuel cell to form a first manifold (5) for incoming fuel gas. A second aligned series of apertures in the fuel cell and separator plates opens from the anode side of each fuel cell to form a second manifold (6) for exhaust fuel gas. A third manifold (7) for in coming air is formed between the stack (3) and housing (4) and opens to the cathode side of each fuel cell. A fourth manifold (8) for exhaust air is formed between the stack (3) and housing (4) and opens from the cathode side of each fuel cell. In a preferred embodiment a third aligned series of apertures in the plates opens from the anode side of each fuel cell to form a second exhaust fuel gas manifold (6) and a second exhaust air manifold (8) is formed between the stack (3) and housing (4). Sliding fibrous seals (9) are provided are provided between the stack (3) and housing (4) to separate the air manifolds (7) and (8).