Technical Abstract: Most of new phosphorus-nitrogen containing compounds were prepared by organic reactions of cyanuric chloride and phosphonates. They were characterized by analytical tools such as proton (1H), carbon (13C), and phosphorus (31P) nuclear magnetic resonance (NMR) spectroscopy and elemental analysis (EA). Cotton twill fabrics were soaked in 10-20% aqueous sodium hydroxide and then treated with organophosphorus or P, N- containing compounds in various organic solvent mixtures. The compounds were grafted onto the fabric by traditional pad, dry, cure methods to produce semi-durable flame resistance. Structural characterizations of treated fabrics were studied by an inductively coupled plasma atomic emission spectroscopy (ICP-AES), elemental analysis (EA), fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Nitrogen is known to have a synergistic effect when combined with phosphorus, resulting in further improvements in char yield. As flame retardant formulations become more complex accurate thermal analysis becomes increasingly important in evaluating and improving new systems. Thermogravimetric analysis (TGA) will provide degradation and char content information of all materials by measuring the change in mass as a function of rising temperature. Treated fabrics were tested for flammability by such methods as modified methenamine pill test, vertical flame test (ASTM D6413-99) and 45 degree angle flame test (ASTM D1230). The limiting oxygen index (LOI, ASTM D2863) test also was used to evaluate flame resistance.