In this study, titanium dioxide (TiO(2)) or nano titanium dioxide (nano-TiO(2)) was used as a cocatalyst in the flame-retardant (FR) formulation of N-methylol dimethylphosphonopropionamide (Pyrovatex CP New, FR), melamine resin [Knittex CHN, crosslinking agent (CL)], and phosphoric acid (PA) for cotton fabrics to improve the treatment effectiveness and minimize the side effects of the treatment. For FR-treated cotton fabrics, the flame extinguished right after removal of the ignition source with no flame spreading. However, after neutralization and/or home laundering, FR-CL-treated specimens failed the flammability test, whereas the opposite results were obtained from FR-CL-PA-treated specimens. A noticeable result was that the TiO(2)/nano-TiO(2) cocatalyst had a significant effect on decreasing the flame-spread rate. Thermal analysis found that the FR-treated specimens without wet posttreatment showed two endothermic peaks representing the phosphorylation of cellulose and acid-catalyzed dehydration. In addition, the treated fabrics showed some new characteristic peaks in their chemical structures; these were interpreted as carbonyl bands, CH(2) rocking bands, and CH(3) asymmetric and CH(2) symmetric stretching. The surface morphology of the FR-CL-PA-treated cotton specimens showed a roughened and wrinkled fabric surface with a high deposition of the finishing agent that had a lower breaking load and tearing strength, which resulted from the side effects of the CL used. However, the addition of a TiO(2) or nano-TiO(2) cocatalyst could compensate for the reduction in the tensile strength. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 267-278, 2011