A simulation code that can model fluid hydrodynamics in permeable media and pleated filter cartridges has been developed and used to evaluate the performance and design of pleated cartridge filter elements. The effects of medium compression, pleat deformation and pleat crowding are analysed. A permeability model that interprets medium compression effects and which is based on data obtained from flat sheets of the filter material used in the fabrication of filter cartridges is incorporated into the main model. During pleating, bending and creasing of the medium deforms it and leads to a loss of permeability and/or effective filtering area. The combined effects of compression and reduction in filtration area cause deviations from Darcy's law. The present work is directed towards the prediction of accurate values of compression factors and percentage losses in the filtration area, which assist in designing pleated cartridge filter elements. The simulated results have been compared against the experimental data for purposes of validation.