The technique of cake forming filtration of suspensions is aimed at optimal separation of solids from the mother liquor. After the filtration step, the filter cake is dewatered and in some in-stance pre-washed. The main parameters required for the assessment of filtration performance are: solids throughput, residual cake moisture content, and in instances where cake washing is necessary, the residual content of the wash out substance and amount of wash liquid used. Due to the complexities of cake formation, washing and dewatering an empirical approach to the design and optimization of the filter apparatus dominates. This approach and its drawbacks are presented. Subsequently, a description of practice oriented mathematical models for all fil-tration steps, and their advantages with respect to characterization of filtration behavior are outlined. Finally it will be shown how using an innovative computer program filter design can be carried out with only a limited number of experiments.