Two N-halamine siloxane precursors, 5,5dimethyl-3-(3'-triethoxysilylpropyl)hydantoin and 3-(31-triethoxysilylpropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]-d ecane-2,4-dione, have been synthesized and coated onto polyester fiber surfaces. The coated polyester was rendered biocidal after exposure to household bleach solution by converting the heterocyclic precursors to N-halamine moieties. The thermal properties of these coated polyester samples were determined with differential scanning calorimetry. The chlorinated polyester swatches were challenged with Staphylococcus aureus (ATCC 6538) and Escherichia coli O157 : H7 (ATCC 43895) with contact times ranging from 1 to 30 min. The biocidal testing showed that the chlorinated samples inactivated S. aureus and E. coli O157 : H7 within 5 and 30 min of contact, respectively. Standard washing tests indicated that the chlorinated coated fibers were very resistant to loss of the coating through hydrolyses. (C) 2008 Wiley Periodicals, Inc.