Acrylamide/maleic acid (AAm/MA) hydrogels prepared by irradiating with gamma-radiation were used in experiments on swelling, diffusion, and uptake of some cationic dyes such as basic red 9 (BR-9), basic green 4 (BG-4), cresyl violet (CV), and basic blue 20 (BB-20). AAm/MA hydrogel containing 60 mg maleic acid and irradiated at 5.71 kGy has been used for swelling and diffusion studies in water and solutions of basic dyes. For this hydrogel, swelling studies indicated that swelling increased in the following order; BR-9 > BG-4 > CV > BB-20 > water. Diffusion of water and the dyes within hydrogels was found to be of a non-Fickian character. The uptake of the cationic dyes to AAm/MA hydrogels is studied by the batch adsorption technique at 25 degrees C. In the adsorption experiments, Langmuir-type adsorption in the Giles classification system was found. Some binding and thermodynamic parameters for AAm/MA hydrogel-dye systems were calculated by using the Klotz method. Adsorption studies indicated that monolayer coverages of AAm/MA hydrogel by these dyes increased in the following order : BB-20 > CV > BG-4 > BR-9.