Models have previously been developed and published to predict the steady-state performance of solid polymer electrolyte membrane fuel cells (PEMFC). In general, such models have been formulated for particular fuel cells and have not been easily applicable to cells with different characteristics, dimensions, etc. The development of a generic model is described here that will accept as input not only values of the operating variables such as anode and cathode feed gas, pressure and compositions, cell temperature and current density, but also cell parameters including active area and membrane thickness. A further feature of the model is the addition of a term to account for membrane ageing. This term is based on the idea that the water-carrying capacity of the membrane deteriorates with time in service. The resulting model is largely mechanistic, with most terms being derived from theory or including coefficients that have a theoretical basis. The major nonmechanistic term is the ohmic overvoltage that is primarily empirically based. The model is applied to several sets of published data for various cells which used platinum as the anode catalyst. Data for various PEM cell designs were well correlated by the model. The lack of agreement of the model predictions with some experimental results may be due to differences in the characteristics of the electrocatalyst. The value of such a generic model to predict or correlate PEM fuel cell voltages is discussed.