Intraparticle transport of amino acids, phenylalanine and tyrosine, in a macroreticular cation-exchange resin, Amberlite 200, was investigated in a finite batch adsorber. A transport model was developed based on the consecutive diffusion of the amino acids through liquid-filled macropores and microspheres. The latter was further simplified by the linear driving force approximation(LDFA) since the microspheres are quite small. The model was used satisfactorily for simulating and predicting the performance of finite batch operations.