NOVELTY - The fuel cell assembly comprises a fuel cell (2), an end plate (4) arranged adjacent to it, a sealing device (6) having a transverse seal and a longitudinal seal for effecting a seal with respect to a gas distributor (5), and a flat sealing element (12) such as a resilient flat sealing element, which is arranged between the sealing device and the end plate. The flat sealing element is permanently fixed to the end plate adjacent to a first end face of same facing the fuel cell and extends toward the second end face of the end plate.    USE - Used as a fuel cell assembly.    ADVANTAGE - The fuel cell assembly can be reliably produced with improved strength.    DETAILED DESCRIPTION - The fuel cell assembly comprises a fuel cell (2), an end plate (4) arranged adjacent to it, a sealing device (6) having a transverse seal and a longitudinal seal for effecting a seal with respect to a gas distributor (5), and a flat sealing element (12) such as a resilient flat sealing element, which is arranged between the sealing device and the end plate. The flat sealing element is permanently fixed to the end plate adjacent to a first end face of same facing the fuel cell and extends toward the second end face of the end plate. At an end adjacent to the second end face, the flat sealing element is permanently loaded by a preload force in a direction from the end plate toward the sealing device. A prestressing device is provided for impacting with the preload force. The preloaded means of the prestressing device is variable. The prestressing device has a cylindrical preload element. The flat sealing element interacts in a sealing with a sealing ramp. The transverse seal of the sealing device of an active sealing surface is developed for contact with the flat sealing element. The longitudinal seal of the sealing device projects in the area of overlapping through the flat sealing element. The end plate has a material reduced region adjacent to the flat sealing element, in which the flat sealing element is immersible during pressing against the active sealing surface. The transverse seal for the formation of the active sealing surface has running ramp surfaces or a curved surface to each other. The active sealing surface is formed by means of a sealing edge. The flat sealing element is applied over its total transverse extending on the active sealing surface. The flat sealing element extends over its total transverse extending of the end plate. The material reduced region enables immersion of the sealing element over its total transverse and is formed as a recess and/or stamp, which is formed in the direction of the first to second face of the end plate adjacent to the first face facing in the end plate. The material reduced region is formed between the end faces of the end plate. The active flat surface is formed by means of ceramic material. The flat sealing element is charged during immersion in the material reduced region against the direction of the second end face of the end plate adjacent to acted preload force. The flat sealing element forms a U-web element of a U-shaped seal. A first U-side of U-shaped seal is fixed between the end plates adjacent to the fuel cell and adjacent to the first face of the end plate. The U-web element of the U-shaped seal extends itself the first face in direction to the second face of the end plate outside the end plate. The U-shaped seal is impinged on end of the U-web element opposite to the first U-web element with the preload force in the direction of the end plate for U-web element by means of the prestressing device. The prestressing element is captured from the second U-side in connection with the end plate and/or the U-shaped web element.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of a fuel cell assembly.    Fuel cell (2)    End plate (4)    Gas distributor (5)    Sealing device (6)    Sealing element. (12)