In this report, the synthesis of a novel superabsorbent hydrogel via gamma-irradiation graft copolymerization of acrylamide onto sodium alginate and kappa-carrageenan hybrid backbones in a homogeneous solution is described. The Taguchi method was used as a powerful experimental design tool for synthesis optimization. A series of superabsorbent hydrogels was synthesized by proposed conditions of Qualitek-4 software. Considering the results of nine trials according to analysis of variance, optimum conditions were proposed. The swelling behavior of optimum superabsorbent hydrogels was studied in various solutions, with pH values ranging from 1 to 13. In addition, swelling kinetics, swelling in various organic solvents, the absorbency under load, and on-off switching behavior were investigated. Also, hydrogel formation was confirmed by Fourier transform infrared spectroscopy. Surface morphology of the synthesized hydrogels was assessed by scanning electron microscopy. (C) 2009 Wiley Periodicals, Inc. Adv Polym Techn 28: 131-140, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20154