Equilibrium isotherms for adsorption of bovine serum albumin (BSA) on the weak base (DEAD) dextran-type and the weak acid (CM) dextran-type ion exchangers were determined experimentally. The constant pH value and ionic strength of BSA solutions respectively remained with different buffers and NaCl, and it was found that the isotherms were affected by pH considerably. Under certain conditions, the kink or step in the adsorption isotherms, i.e. the stepwise nature for BSA adsorption was observed. From the comparison between the adsorption properties of BSA on DEAE- and CM-ion-exchange resins, the adsorption mechanism of BSA on dextran-type ion exchangers was discussed.