pH-sensitive poly(acrylamide-co-itaconic acid) [P(AAm/IA)] hydrogels were prepared by radiation induced copolymerization of acrylamide (AAm) and itaconic acid (IA) at various ratios. Swelling and shrinking behaviors of these hydrogels were found greatly dependent on the composition of the hydrogel and pH of the buffer solution. The basic structural parameters of the P(AAm/IA) networks such as the molecular weight between crosslinks ((M) over bar (c)) and polymer-solvent interaction parameter (chi) were also determined using the modified Flory-Rehner equations. (C) 2004 Wiley Periodicals, Inc.