Suitable buffer additives can either induce or reduce the electrophoretic mobility of certain polysaccharides during capillary electrophoresis. With water-soluble cellulose derivatives, adsorption of detergents on the analyte molecules governs the migration rates. Different types of adsorption sites, including multilayer formation, were found to be present on the cellulose-derived polymers. For highly charged polysaccharides (heparins), the electrophoretic mobility can be controlled by the use of ion-pairing reagents. The concentration and number of cationic charges appear useful in optimizing the separation selectivity. Migration models based on secondary thermodynamic equilibria are presented and evaluated for different polysaccharides.