Liquid chromatography has been used to evaluate the sorption and diffusion characteristics of DL-tryptophan, DL-phenylalanine, L-DOPA, DL-glutamic acid, and DL-lysine in modified divinylbenzene-polystyrene resins. All amino acids adsorbed quite rapidly, but there were significant differences in both equilibrium constants and diffusivities. On the modified resins, the values of equilibrium constants decreased with decreasing molecular weight. Diffusivity values increased with temperature and decreased with molecular weight for both resins.