In vitro swelling and in vivo biocompatibility of radiation induced acrylamide (AAm) and acrylamide/maleic acid (AAm/MA) hydrogels were investigated. The swelling kinetics of AAm and AAm/MA hydrogels of are investigated in distilled water, human serum and some simulated physiological fluids such as phosphate buffer at pH 7.4, glycine-HCl buffer at pH 1.1, physiological saline solution and, some swelling and diffusion parameters have been calculated. AAm and AAm/MA hydrogels were subcutaneously implanted in rats for up to 10 weeks and the tissue response to these implants was studied. Histological analysis indicated that tissue reaction at the implant site progressed from an initial acute inflammatory response characterized. No necrosis, tumorigenesis or infection was observed at the implant site up to 10 week. In vivo studies indicated that the radiation induced acrylamide and acrylamide/maleic acid hydrogels were found to be well-tolerated, non-toxic and highly biocompatible. (C) 2001 Kluwer Academic Publishers.