Polypropylene/silver composites were subjected to silver ion release experiments in order to investigate their Ag+ release capabilities, a pertinent condition for antimicrobial efficacy. Polypropylene containing elementary silver powder having a specific surface area of 0.78 m(2)/g was considered as the principal antimicrobial filler. In addition. the effectiveness of other commercial antimicrobials based on silver were also examined. Evidence is presented for the release of silver ions from these composites in an aqueous environment. The silver ion release depends on the nature of the antimicrobial filler and the polymer matrix. Scanning electron microscopy has been employed to investigate the morphology of the composite and they were found to be active against the microbes. An excellent correlation between the silver ion release experiments and the antimicrobial efficacy was found. Multifilament yarns produced from polypropylene containing elementary silver powder show excellent long term Ag+ release properties. (C) 2005 Elsevier B.V. All rights reserved.