The feasibility of using chitosan as a thickener in the pretreatment print paste for textile ink-jet printing was explored. An orthogonal analysis was used to determine the optimum conditions for using chitosan as a thickener in the pretreatment print paste and the effects of different process factors for achieving the best color yield in textile ink-jet printing. With the help of the orthogonal analysis, the importance of different process factors was found to be in the order of (1) the amount of urea used, (2) the amount of chitosan used, (3) the amount of sodium bicarbonate used, and (4) the steaming time. On the basis of the results of the orthogonal analysis, the optimum conditions for using chitosan as a thickener for the pretreatment print paste were concluded to be 40 mL of chitosan, 10 g of urea, 8 g of sodium bicarbonate, and 5 min of steaming. According to an analysis of the results of different color fastness tests, chitosan could principally work as a pretreatment print paste thickener. However, the final color yield obtained from chitosan-containing cotton fabrics depended greatly on the stage of the chitosan application. Nevertheless, the color fastness properties and the outline sharpness of the prints of cotton fabric were greatly improved by the chitosan treatment. A two-bath chitosan treatment was developed to separate the chitosan from sodium bicarbonate and urea before it was padded onto the fabric surface to minimize the neutralization effect. On the basis of the results for the highest color yield obtained on the cotton fabric, it was confirmed that the two-bath chitosan treatment was successfully developed. In addition, chitosan could impart higher antibacterial properties with a slight reduction in the tensile strength of the cotton fabric. (C) 2007 Wiley Periodicals, Inc.