In this study, antibacterial properties were induced in polyurethane (PU) films by the incorporation of Ag+-loaded zeolites as fillers. The mechanical and thermal properties of the prepared composites were also investigated. For this purpose, two different types of zeolite microparticles, high-silica zeolite beta crystals and low-silica zeolite A crystals, were synthesized. Ag+ was added by ion exchange, and these particles were incorporated into the PU prepolymer, which was prepared from its main components of toluene diisocyanate and polypropylene ethylene glycol (medical purity). Microbiological tests revealed that both types of composites, prepared by the addition of Ag+-containing zeolite beta or zeolite A to the PU matrix, had antibacterial properties. It was demonstrated for the first time that a high-silica zeolite (zeolite beta) and its composite film could be effectively employed as antibacterial materials. Furthermore, mechanical and thermal characterization of the composites showed that the zeolites enhanced the mechanical properties of the polymer and did not cause any deterioration in its thermal properties. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2854-2861, 2008