Microbial contamination on medical device material surfaces causes serious problems including device-related infections. Here we report a new strategy to produce rechargeable antimicrobial biomaterial surfaces to address the issue. Methacrylic acid (MAA) was grafted onto the surfaces of polyurethane (PU), a widely used biomaterial with excellent biological and mechanical properties. Chitosan was covalently bonded onto the MAA-grafted surfaces. The new chitosan-containing PU strongly bound and then slowed release anionic antibiotics (e.g., rifampin) for weeks to months to kill microbes. The released drug could be recharged with the same or a different class of drugs to further extend antimicrobial duration. Also, the new surfaces demonstrated good biocompatibility against mammal cells, pointing to great potentials for a wide range of biomedical applications. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.