Quaternary aminopyridinium salts were employed in antimicrobial finishing wool fabrics. The effects of alkyl chain length in the salts, pH conditions of finishing baths, finishing time and temperature, and salt concentrations were investigated. The incorporated quaternary aminopyridinium salt molecules on wool were characterized by FTIR. The quaternary ammonium salt could form ionic interactions with anionic groups on wool, which contribute to the durable antimicrobial functions. All the finished wool fabrics exhibited antimicrobial efficacy against Escherichia coli. The washing durability of antimicrobial functions on the finished wool fabrics was also studied. (c) 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 482-486, 2007