A theoretical model has been developed to simulate the operation of a dual-piston pressure swing adsorption (PSA) system. In contrast to previous models for this type of system, the pressure variation is calculated directly from the specified movement of the pistons. The predictions of the simulation are compared with experimentally observed pressure profiles under various operating conditions. The model provides a good qualitative prediction of the system behaviour, although the experimental pressure profiles are generally somewhat attenuated relative to the predicted profiles. At slow speeds there is little phase difference between the experimental profiles and the theoretical profiles calculated assuming local equilibrium, but for faster cycles (>10 rpm) phase lags become increasingly evident, suggesting the progressive intrusion of mass transfer resistance.