The mechanical behavior of a fuel cell stack was examined. It is important to maintain a suitable contact pressure distribution of the BP (Bipolar Plate), since the contact pressure affects the power efficiency of the fuel cell stack. A general procedure is described for determining the pressure distribution of a BP. Ten BPs are used to analyze the overall stack behavior. Gasket behavior was obtained by modeling the effects of thermal aging. Using Arrhenius' equation, the gasket behavior after five years was estimated. The results are applied to estimate fuel cell stack behavior after five years.