Abstract A process is investigated quantitatively for concentrating dilute aqueous bovine serum albumin solutions with superabsorbent crosslinked hydrogels. In the process, the gel swells by absorbing water only while macromolecules are excluded, thus producing a concentrated retentate. The concentration of the retentate is about 5.8 times larger than that of the feed for a dosage of dry gels of 0.63% by weight. The dynamic behavior of the concentration process is described by using the equation of motion of the gel network on the basis of the kinetics of the swelling of the gel. The pore size of the hydrogen controlling the sieving property is estimated from measurements of the permeation rate of water through the compressed, packed bed of the swelling gels, known as the compression-permeability test. It is demonstrated that slight stirring during the concentration process is accompanied by a rapid removal of the BSA filter cake on the gel surface, leading to efficient concentration.