A new method for the determination of the yellowing tendency of cotton cellulose is presented. It consists in extracting the sample in a 5% sodium bicarbonate solution under reflux for one hour and measuring the color intensity of the yellow solutions obtained. The solutions strictly obey Beer’s Law. The color intensity is proportional to the solubility during extraction and is linearly related to the amount of cotton used in the extraction and to the extent of hydrolytic or oxidative modification of the cellulose. The influence of the extraction time and of the storage time of the extracts on color intensity is studied.