Bleaching is an important step of textile processes which improves the absorbance properties of cotton fibres. Conventional method has some difficulties such as higher time and energy, water consumption and damaging the ecology. The use of ultrasonic energy in textiles, might impart a new improvement to a bleaching process. This paper is about the hydrogen peroxide bleaching of cotton fibres and cotton spun yams using of ultrasonic energy. The method solves most of the difficulties in bleaching, i.e. reducing time and decreasing energy consumption. In this work, first a variety of Turkish raw cottons were treated with H2O2 at different temperatures and times and later, 100% cotton spun yams (Ne22) produced from these cottons were bleached with hydrogen peroxide again at different temperatures and times in a ultrasonic bath. The results of the bleached cottons and bleached yams were also analysed spectrophotometrically.