Ozone is a powerful oxidizing agent and is widely used in various applications, which includes bleaching of cotton. Literature on the action of ozone on silk is almost not available. Therefore, an elaborate study was carried out to understand the effects of process parameters in the ozone treatment of raw and degummed tassar silk fabrics on their properties. The study was extended with a view to compare the ozone treatment with soap degumming and hydrogen peroxide treatment carried out on raw and degummed tassar silk fabrics, respectively. The treatment results in improvement in pliability of the fabric and reduction in color. Decrease in breaking strength, breaking elongation, and weight as well an increase in amino group content is also experienced by the material. The results obtained are substantiated with tyrosine content, scanning electron micrographs, and infrared spectroscopy of the treated materials. The effect of pH on the treatment is maximum upto pH 4 and then decreases. The treatment is more severe when the wet pickup used is 50% compared to 10 and 100%. With respect to treatment time, though the severity increases with time, it is maximum during the first 10 min of the treatment. Soap degumming of raw silk fabric results in little higher yellowness index and lesser loss in breaking strength and elongation and flexural rigidity compared to that of ozone-treated material. There is not much of difference between ozone and hydrogen peroxide treatments of degummed silk fabric, except for the lesser yellowness index obtained in the latter case. (c) 2007 Wiley Periodicals, Inc.