A simulation model describing L-lysine behavior in multicolumn cation exchange separation was developed and used to investigate the effect of column number in adsorption and desorption of counter-current multi-column systems. DIMON SK-1B was used as an example of cation exchange resin, which has 8% of DVB content. L-lysine dissociation constants, ion exchange equilibrium constants and intraparticle diffusivities were measured at 25 degrees C. These fundamental parameters were applied for multicolumn simulation. All calculated results were obtained for a column of 1.5 cm phi X 10 cm and switching time of 3600 s. 1. In the case of single-column adsorption, L-lysine leakage in the adsorption train was observed at a feed rate of 5.7X 10(-2) mol/h of L-lysine when monovalent lysine solution was fed to the multicolumn system. Two-and three-column adsorption systems showed L-lysine leakage at feed rates of 1.2x10(-1) mol/h and 1.4 X 10(-1) mol/h of L-lysine, respectively. Thus, the increase of column number from 1 to 2 was effective for prevention of the leakage, while the increase of column number from 2 to 3 was not effective. 2. In the case of single-column elution, L-lysine was not completely desorbed at any feed rate of ammonia into the system. Two- and three-column desorption systems showed similar results, with complete L-lysine desorption at feed rates of 6.6X 10-2 mol/h and 1.0X 10(-1) mol/h of ammonia, respectively.