Antimicrobial treatments of textiles have received substantial attention in recent years, both in academic research and in commercial productions. Such treatments prevent the odor formation and fabric deterioration that arise from the growth of microbes on the textiles during their use or storage. So far, antimicrobial treatments have mainly focused on cotton and synthetic fibers, and a viable treatment for wool is lacking. in this report, we demonstrate a novel and effective antimicrobial finishing for wool. We found that pretreatment with peroxymonosulfate and sulfite, a treatment previously developed for shrink resistance, uniquely enabled wool to exhaust up to 5% (on the weight of the fabric) of the biocide polyhexamethylene biguanide (PHMB) under mild conditions. In contrast, untreated or chlorinated wool had little affinity for this biocide. The exhaustion was facilitated by higher temperatures but was not affected by pH over a broad range. Wool fabrics finished with PHMB exhibited strong antimicrobial abilities that could deactivate the bacterium Escherichia coli within a few minutes of contact. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 3075-3082, 2010