Cellulases are widely used to age denim fabrics. In this work the effects of three purified monocomponent cellulases, EG I, EG II, and CBH I, and two different cellulase mixtures produced by genetically modified strains of Trichoderma reesei are compared for stone washing denim fabrics. Stone washing effects are evaluated by analyzing the soluble reducing sugars, absorbance, and lightness values of the treatment solutions. The prop erties of denim swatches are evaluated by reflectance units and by a panel. Purified cellulase EG II is most effective at removing color from denim, producing a good stone washing effect with the lowest hydrolysis level. Treatment with CBH I does not produce any stone washing effect, even at high enzyme dosages. The commercial cellulase Ecostone® L produces a good stone washing effect, but the experimental cellulase mixture Cellulase B removes color only with the highest enzyme dosage, i.e., when the amount of EGS in the mixture is high enough.