Poly(acrylamide-co-2-acrylamido-2-methyl-propane sulfonic acid) hydrogels were synthesized using gamma-radiation-initiated polymerization. The progress of copolymerization and crosslinking was observed by viscosity measurement on reaction mixtures subjected to varying radiation doses. The copolymer gels were characterized by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and elemental analysis. The swelling behavior and other properties of the gels were found to be very similar to those of poly(acrylamide-co-2-acrylamido-2-methyl-propane sulfonic acid) hydrogels synthesized using conventional free-radical initiation in the presence of crosslinkers. (C) 2003 Wiley Periodicals, Inc.