In this study the grafting of acrylamide onto poly(ethylene terephthalate) fibers with the help of benzoyl peroxide and the effects of the temperature and the concentrations of initiator and monomer were investigated. Some of the experiments were repeated several times in order to check the reproducibility. The optimum temperature for grafting was found to be 75°C. The graft yield was observed to increase with the monomer concentrations examined. The graft yield increased up to the benzoyl peroxide concentration approximately 0.05 g/50 mL, and then passed a plateau, before showing a decrease. The fiber diameter, intrinsic viscosity, and the moisture regain increased while the fiber density decreased with the graft yield.