Silver nanoparticles were immobilized on the surface of polypropylene (PP) porous beads by an ultrasound-assisted reduction method. The structure and properties of the silver-PP composite were characterized with XRD, TEM, HRSEM, EDX, XPS, and Raman spectroscopy. Water-soluble polymers such as PEG, PVA, and PVP were used as stabilizing agents for preventing the agglomeration of the silver nanoparticles. With PVP, a homogeneous distribution of silver nanocrystals, 50 nm in size, on the PP surface was achieved. The mechanism proposed for the silver anchoring to the inert polymer accounts for a localized melting of the PP. The beads of the silver PP composite demonstrated good stability and high antibacterial activity. (c) 2008 Wiley Periodicals, Inc.