Antimicrobial efficacy of irradiated gentimicin was compared with the control and effect of the irradiation on potency of the gentamicin was studied. Hydrogel films containing gentamicin were prepared by radiation crosslinking technique, and mechanisms of the drug release ,in vitro, were studied. The results indicated that potency of the gentamicin irradiated to 37.5kGy did not change. The hydrogel films incorporated gentamicin before the irradiation released gentamicin to peak during 12h, while the hydrogel films incorporated gentamicin after irradiation released gentamicin to peak during 8h. The drug released slowly up to 5d. The drug delivery conformed to Higuchi kinetic equation, and mechanisms of the drug release were matrix diffusion. By comparison, the hydrogel films incorporated gentamicin before irradiation released the drug more completely.