An aqueous dispersion of nano-titanium dioxide (nano-TiO2) was prepared and mixed with a silicone softener to establish a finishing bath. Cotton fabrics were treated with this finishing bath with a pad-dry-cure process and were then characterized by X-ray diffraction and scanning electron microscopy. The gaseous ammonia was derived from an environmental condition simulated chamber. The specifically designed photocatalytic reactor was used to assess the factors, including the dosage of the aqueous dispersion of nano-TiO2, the nature of the fabric, the direct dye, and the water-repellent agent, that affected the decomposition efficiency of ammonia in air. In addition, nano-TiO2-finished fabrics were evaluated with respect to whiteness and breaking tension properties. (c) 2005 Wiley Periodicals, Inc.