The Simulated Moving. Bed process is a powerful tool for continuous separation of multicomponent mixtures in which the components have different adsorption affinities. It is suitable for a broad range of preparative or production scale applications and allows the separation of components with separation factors near unity with high resolution, yield and purity. Furthermore, the desorbent rates and the amount of adsorbent required by Simulated Moving Bed processes are much lower than those for corresponding batch pocesses. The SMB-process is subject to different parameters specifying plant size, operating conditions and process variables. Precise simulations are therefore necessary for process design and evaluation of experimental results. Different rigorous models which describe the chromatographic process in terms of either moving beds with steady state countercurrent flow or simulated moving beds with periodic fluid port switching have been evaluated. The results demonstrate that because of the real periodic flow SMB-processes must be described by rigorous dynamic models with tubular reactor units and fluid port switching. Axial dispersion and mass transfer resistance have to be taken into account in order to obtain a good agreement with experimental results. The detailed dynamic model which has been developed makes it possible to understand malfunctions of pilot plants, to optimise process conditions and to specify startup procedures for SMB-processes.