We prepared polymeric N-halamine/silver nanoparticle composites to develop new effective biocidal systems. They were synthesized by mixing poly[oxy[(3-chloro-4,4-dimethyl-imidazolelidine-2,5-dionyl)methyl]ethylene](POCE) with silver perchlorate followed by UV reduction. These composites exhibit potent antibacterial activity against the gram-negative bacteria, Escherichia coli.