2,2,5,5-Tetramethylimidazolidinone (TMIO)-modified cotton-containing fabrics could provide excellent durable antimicrobial properties, but the biocidal speeds were low because of its amine halamine structures. To prepare biocidal fabrics that can inactivate microorganisms rapidly and survive repeated laundering and long duration of storage, 3-methylol-2,2,5,5-tetramethylimidazolidinone and dimethylol-5,5-dimethylhydantoin were combined in different ratios in chemical modifications of cellulose fabrics. The mixtures of TMIO and hydantoin rings on the grafted cellulose provided a hybrid of imide, amide, and amine halamine structures in different ratios after chlorination, and led to varied efficacy and durability of biocidal properties on the finished fabrics. The effect of the combined halamine structures on biocidal efficacy and durability of the fabrics were discussed in this article. (C) 2003 Wiley Periodicals, Inc.