Poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS)/hyaluronic acid (HA) interpenetrating polymer network (IPN) hvdrogels have been prepared by using the sequential-IPN method. The IPN hydrogels exhibited swelling behavior in solutions at various pHs, in NaCl solutions, and under electrical DC stimulation. The IPN hydrogels were highly swollen in water, but lost much of their water capacity when transferred to solutions having a high ionic strength. The IPN hydrogels showed a significant responsive deswelling in an applied electric field. This behavior indicates the potential application of IPN hydrogels as biomaterials. (C) 2004 Wiley Periodicals, Inc.