The invention relates to bipolar plates for fuel cell systems. According to the invention, the component sheets of a bipolar plate (1) are formed for a welded joint (4, 5), such that between the profile regions (6) of the channel ducts (2), only small local surfaces remain as welding zones (10). The above is achieved by means of a corresponding shape of the profile molding (8, 9) of the component sheets. As a result of said reduction of the welding zones to small regions of the total surface, a larger proportion of the area is available for the channels (2), in other words, the channel cross-section and hence the coolant flow can be increased. At the same time the structure for the use of gas diffusion layers made from non-wovens, textiles or paper can be optimized.