The filtration data obtained from pressure filtration experiments with a gradual pressure increase have been interpreted by a data evaluation program, which takes into consideration the pressure drop in the filter medium and the sedimentation of the slurry. The structures of the filter cakes were surveyed by additional particle size measurements. The results showed that the specific filtration resistance and its pressure dependence can be obtained in a single filtration test with a gradual increase in pressure, compared with several tests at different constant pressures.