A mixture of acrylamide (AAm) and itaconic acid (IA) was grafted onto poly(ethylene terephthalate) (PET) fibers with benzoyl peroxide in aqueous media. The effects of polymerization conditions such as the temperature, polymerization time, initiator concentration, and monomer mixture ratio on grafting were investigated. The maximum graft yield was 76.1% with an AAm/IA mixture ratio of 90/10 (mol/mol). The graft yield was as low as 3% in the single grafting of IA, whereas the use of AAm as a comonomer increased the amount of TA that entered the fiber structure to 33.5%. An increase in the temperature from 65 to 85 degrees C increased the grafting rate and saturation graft yield. However, an increase in the temperature above 85 degrees C decreased the saturation graft yield. The graft yield increased up to an initiator concentration of 1.0 X 10(-2) M and decreased afterwards. The grafting rate was 0.65th- and 0.74th-order with respect to the initiator and AAm concentrations, respectively. The densities, diameters, and moisture-regain values of the AAm/IA-grafted PET fibers increased with the graft yield. Similarly, there was an increase in the dyeability of the AAm/IA-grafted fibers with acidic and basic dyes. The grafted fibers were characterized with Fourier transform infrared and thermogravimetric analysis, and their morphologies were examined with scanning electron microscopy. (C) 2005 Wiley Periodicals, Inc.