Theoretical analysis has been presented to estimate the kinetic characteristics, the magnitude of which determines the efficiency of preparative ion-exchange chromatography. The nonlinear problem of ion-exchange kinetics with an interdiffusion coefficient depending on the ionite phase composition has been discussed. The case of both film and intraparticle diffusion control has been considered. The interrelation between the effective diffusion coefficients and those of counterion diffusion has been determined. This has enabled estimation of the values of the self-diffusion coefficients of oxytetracycline and chlortetracycline using the experimental values of the effective diffusion coefficients.