Phosphoramide containing an active vinyl group (P-III) was prepared. Its structure was confirmed by elemental analysis and Fourier transform infrared, nuclear magnetic resonance, and mass spectroscopy. P-III was evaluated as a fire-retardant finishing agent for cotton fabrics. It was applied to cotton fabrics using a graft process with an Fe2+/H2O2 redox system. The major factors affecting the reaction were studied. The finished cotton fabrics were examined for flammability, and the effect of washing on treated fabrics was also examined. The results showed that P-III can be successfully used as a flame retardant for cotton fabrics. Durably flame-retardant cotton fabrics were obtained at add-on levels higher than 38%. (C) 2003 Wiley Periodicals, Inc.